diff --git a/Resources/Icons/Selection.png b/Resources/Icons/Selection.png
new file mode 100644
index 00000000..486d40ce
Binary files /dev/null and b/Resources/Icons/Selection.png differ
diff --git a/Resources/Icons/SelectionApply.png b/Resources/Icons/SelectionApply.png
new file mode 100644
index 00000000..8bb24ee0
Binary files /dev/null and b/Resources/Icons/SelectionApply.png differ
diff --git a/Resources/Icons/mergegeometry.png b/Resources/Icons/mergegeometry.png
new file mode 100644
index 00000000..c9c44274
Binary files /dev/null and b/Resources/Icons/mergegeometry.png differ
diff --git a/Resources/Icons/mergegeometry2.png b/Resources/Icons/mergegeometry2.png
new file mode 100644
index 00000000..f8af3f15
Binary files /dev/null and b/Resources/Icons/mergegeometry2.png differ
diff --git a/Resources/mergegeometry.cpt b/Resources/mergegeometry.cpt
new file mode 100644
index 00000000..0a7b1f1b
Binary files /dev/null and b/Resources/mergegeometry.cpt differ
diff --git a/Source/Builder.csproj b/Source/Builder.csproj
index 5cf1fbb8..c3328978 100644
--- a/Source/Builder.csproj
+++ b/Source/Builder.csproj
@@ -284,6 +284,8 @@
   </ItemGroup>
   <ItemGroup>
     <Content Include="Resources\Builder.ico" />
+    <None Include="Resources\mergegeometry2.png" />
+    <None Include="Resources\mergegeometry.png" />
     <None Include="Resources\Grid4.png" />
     <None Include="Resources\Redo.png" />
     <None Include="Resources\Undo.png" />
diff --git a/Source/Config/ProgramConfiguration.cs b/Source/Config/ProgramConfiguration.cs
index e0455098..eb9cff57 100644
--- a/Source/Config/ProgramConfiguration.cs
+++ b/Source/Config/ProgramConfiguration.cs
@@ -43,6 +43,7 @@ namespace CodeImp.DoomBuilder.Config
 		private Configuration cfg;
 		
 		// Cached variables
+		private int undolevels;
 		private bool blackbrowsers;
 		private float stitchdistance;
 		
@@ -51,6 +52,7 @@ namespace CodeImp.DoomBuilder.Config
 		#region ================== Properties
 
 		public Configuration Config { get { return cfg; } }
+		public int UndoLevels { get { return undolevels; } set { undolevels = value; } }
 		public bool BlackBrowsers { get { return blackbrowsers; } set { blackbrowsers = value; } }
 		public float StitchDistance { get { return stitchdistance; } set { stitchdistance = value; } }
 
@@ -78,6 +80,7 @@ namespace CodeImp.DoomBuilder.Config
 				// Read the cache variables
 				blackbrowsers = cfg.ReadSetting("blackbrowsers", false);
 				stitchdistance = cfg.ReadSetting("stitchdistance", 2.0f);
+				undolevels = cfg.ReadSetting("undolevels", 20);
 
 				// Success
 				return true;
@@ -95,6 +98,7 @@ namespace CodeImp.DoomBuilder.Config
 			// Write the cache variables
 			cfg.WriteSetting("blackbrowsers", blackbrowsers);
 			cfg.WriteSetting("stitchdistance", stitchdistance);
+			cfg.WriteSetting("undolevels", undolevels);
 
 			// Save settings configuration
 			General.WriteLogLine("Saving program configuration...");
diff --git a/Source/Controls/ActionManager.cs b/Source/Controls/ActionManager.cs
index be0887bd..ffe71447 100644
--- a/Source/Controls/ActionManager.cs
+++ b/Source/Controls/ActionManager.cs
@@ -48,7 +48,7 @@ namespace CodeImp.DoomBuilder.Controls
 
 		#region ================== Properties
 
-		public Action this[string action] { get { return actions[action]; } }
+		public Action this[string action] { get { if(actions.ContainsKey(action)) return actions[action]; else throw new ArgumentException("There is no such action \"" + action + "\""); } }
 		public bool IsDisposed { get { return isdisposed; } }
 
 		#endregion
diff --git a/Source/Editing/DragVerticesMode.cs b/Source/Editing/DragVerticesMode.cs
index 305cb36e..74597405 100644
--- a/Source/Editing/DragVerticesMode.cs
+++ b/Source/Editing/DragVerticesMode.cs
@@ -225,7 +225,6 @@ namespace CodeImp.DoomBuilder.Editing
 		{
 			ICollection<Linedef> movinglines;
 			ICollection<Linedef> fixedlines;
-			ICollection<Linedef> changedlines;
 			Rectangle editarea;
 			int stitches = 0;
 			int stitchundo;
@@ -246,44 +245,45 @@ namespace CodeImp.DoomBuilder.Editing
 				MoveGeometryRelative(mousemappos - dragstartmappos, snaptogrid, snaptonearest);
 
 				// ===== BEGIN GEOMETRY STITCHING
-				
-				// Make undo for the stitching
-				stitchundo = General.Map.UndoRedo.CreateUndo("stitch geometry", UndoGroup.None, 0, false);
+				if(General.MainWindow.AutoMerge)
+				{
+					// Make undo for the stitching
+					stitchundo = General.Map.UndoRedo.CreateUndo("stitch geometry", UndoGroup.None, 0, false);
 
-				// Find lines that moved during the drag
-				movinglines = General.Map.Map.LinedefsFromSelectedVertices(false, true, true);
-				
-				// Find all non-moving lines
-				fixedlines = General.Map.Map.LinedefsFromSelectedVertices(true, false, false);
-				
-				// Determine area in which we are editing
-				editarea = MapSet.AreaFromLines(movinglines);
-				editarea.Inflate((int)Math.Ceiling(General.Settings.StitchDistance),
-					             (int)Math.Ceiling(General.Settings.StitchDistance));
+					// Find lines that moved during the drag
+					movinglines = General.Map.Map.LinedefsFromSelectedVertices(false, true, true);
 
-				// Join nearby vertices
-				stitches += MapSet.JoinVertices(unselectedverts, selectedverts, true, General.Settings.StitchDistance);
+					// Find all non-moving lines
+					fixedlines = General.Map.Map.LinedefsFromSelectedVertices(true, false, false);
 
-				// Update cached values
-				General.Map.Map.Update();
-				
-				// Split moving lines with unselected vertices
-				unselectedverts = MapSet.FilterArea(unselectedverts, ref editarea);
-				stitches += MapSet.SplitLinesByVertices(movinglines, unselectedverts, General.Settings.StitchDistance, movinglines);
-				
-				// Split non-moving lines with selected vertices
-				fixedlines = MapSet.FilterArea(fixedlines, ref editarea);
-				stitches += MapSet.SplitLinesByVertices(fixedlines, selectedverts, General.Settings.StitchDistance, movinglines);
+					// Determine area in which we are editing
+					editarea = MapSet.AreaFromLines(movinglines);
+					editarea.Inflate((int)Math.Ceiling(General.Settings.StitchDistance),
+									 (int)Math.Ceiling(General.Settings.StitchDistance));
 
-				// Remove looped linedefs
-				stitches += MapSet.RemoveLoopedLinedefs(movinglines);
+					// Join nearby vertices
+					stitches += MapSet.JoinVertices(unselectedverts, selectedverts, true, General.Settings.StitchDistance);
 
-				// Join overlapping lines
-				stitches += MapSet.JoinOverlappingLines(movinglines);
+					// Update cached values
+					General.Map.Map.Update();
 
-				// No stitching done? then withdraw undo
-				if(stitches == 0) General.Map.UndoRedo.WithdrawUndo(stitchundo);
+					// Split moving lines with unselected vertices
+					unselectedverts = MapSet.FilterArea(unselectedverts, ref editarea);
+					stitches += MapSet.SplitLinesByVertices(movinglines, unselectedverts, General.Settings.StitchDistance, movinglines);
 
+					// Split non-moving lines with selected vertices
+					fixedlines = MapSet.FilterArea(fixedlines, ref editarea);
+					stitches += MapSet.SplitLinesByVertices(fixedlines, selectedverts, General.Settings.StitchDistance, movinglines);
+
+					// Remove looped linedefs
+					stitches += MapSet.RemoveLoopedLinedefs(movinglines);
+
+					// Join overlapping lines
+					stitches += MapSet.JoinOverlappingLines(movinglines);
+
+					// No stitching done? then withdraw undo
+					if(stitches == 0) General.Map.UndoRedo.WithdrawUndo(stitchundo);
+				}
 				// ===== END GEOMETRY STITCHING
 
 				// If only a single vertex was selected, deselect it now
diff --git a/Source/Editing/UndoManager.cs b/Source/Editing/UndoManager.cs
index 33c66e8c..5972fed0 100644
--- a/Source/Editing/UndoManager.cs
+++ b/Source/Editing/UndoManager.cs
@@ -44,8 +44,8 @@ namespace CodeImp.DoomBuilder.Editing
 		#region ================== Variables
 
 		// Undo and redo stacks
-		private Stack<UndoSnapshot> undos;
-		private Stack<UndoSnapshot> redos;
+		private List<UndoSnapshot> undos;
+		private List<UndoSnapshot> redos;
 
 		// Grouping
 		private UndoGroup lastgroup;
@@ -61,8 +61,8 @@ namespace CodeImp.DoomBuilder.Editing
 
 		#region ================== Properties
 
-		public UndoSnapshot NextUndo { get { if(undos.Count > 0) return undos.Peek(); else return null; } }
-		public UndoSnapshot NextRedo { get { if(redos.Count > 0) return redos.Peek(); else return null; } }
+		public UndoSnapshot NextUndo { get { if(undos.Count > 0) return undos[0]; else return null; } }
+		public UndoSnapshot NextRedo { get { if(redos.Count > 0) return redos[0]; else return null; } }
 		public bool IsDisposed { get { return isdisposed; } }
 
 		#endregion
@@ -74,8 +74,8 @@ namespace CodeImp.DoomBuilder.Editing
 		{
 			// Initialize
 			ticketid = 1;
-			undos = new Stack<UndoSnapshot>();
-			redos = new Stack<UndoSnapshot>();
+			undos = new List<UndoSnapshot>(General.Settings.UndoLevels + 1);
+			redos = new List<UndoSnapshot>(General.Settings.UndoLevels + 1);
 
 			// Bind any methods
 			ActionAttribute.BindMethods(this);
@@ -122,6 +122,21 @@ namespace CodeImp.DoomBuilder.Editing
 			undos.Clear();
 		}
 
+		// This checks and removes a level when the limit is reached
+		private void LimitUndoRedoLevel(List<UndoSnapshot> list)
+		{
+			UndoSnapshot u;
+			
+			// Too many?
+			if(list.Count > General.Settings.UndoLevels)
+			{
+				// Remove one and dispose map
+				u = list[list.Count - 1];
+				u.map.Dispose();
+				list.RemoveAt(list.Count - 1);
+			}
+		}
+
 		#endregion
 		
 		#region ================== Public Methods
@@ -143,8 +158,9 @@ namespace CodeImp.DoomBuilder.Editing
 				u = new UndoSnapshot(description, allow3dchange, General.Map.Map.Clone(), ticketid);
 
 				// Put it on the stack
-				undos.Push(u);
-
+				undos.Insert(0, u);
+				LimitUndoRedoLevel(undos);
+				
 				// Clear all redos
 				redos.Clear();
 
@@ -171,10 +187,10 @@ namespace CodeImp.DoomBuilder.Editing
 			if(undos.Count > 0)
 			{
 				// Check if the ticket id matches
-				if(ticket == undos.Peek().ticketid)
+				if(ticket == undos[0].ticketid)
 				{
 					// Remove the last made undo
-					undos.Pop();
+					undos.RemoveAt(0);
 					
 					// Update
 					General.MainWindow.UpdateInterface();
@@ -192,14 +208,16 @@ namespace CodeImp.DoomBuilder.Editing
 			if(undos.Count > 0)
 			{
 				// Get undo snapshot
-				u = undos.Pop();
+				u = undos[0];
+				undos.RemoveAt(0);
 
 				// Make a snapshot for redo
 				r = new UndoSnapshot(u, General.Map.Map.Clone());
 
 				// Put it on the stack
-				redos.Push(r);
-
+				redos.Insert(0, r);
+				LimitUndoRedoLevel(redos);
+				
 				// Reset grouping
 				lastgroup = UndoGroup.None;
 				
@@ -222,14 +240,16 @@ namespace CodeImp.DoomBuilder.Editing
 			if(redos.Count > 0)
 			{
 				// Get redo snapshot
-				r = redos.Pop();
+				r = redos[0];
+				redos.RemoveAt(0);
 
 				// Make a snapshot for undo
 				u = new UndoSnapshot(r, General.Map.Map.Clone());
 
 				// Put it on the stack
-				undos.Push(u);
-
+				undos.Insert(0, u);
+				LimitUndoRedoLevel(undos);
+				
 				// Reset grouping
 				lastgroup = UndoGroup.None;
 
diff --git a/Source/Interface/MainForm.Designer.cs b/Source/Interface/MainForm.Designer.cs
index fffe11f0..240ff9f1 100644
--- a/Source/Interface/MainForm.Designer.cs
+++ b/Source/Interface/MainForm.Designer.cs
@@ -86,6 +86,7 @@ namespace CodeImp.DoomBuilder.Interface
 			this.thingfilters = new System.Windows.Forms.ToolStripComboBox();
 			this.toolStripSeparator8 = new System.Windows.Forms.ToolStripSeparator();
 			this.buttonsnaptogrid = new System.Windows.Forms.ToolStripButton();
+			this.buttonautomerge = new System.Windows.Forms.ToolStripButton();
 			this.statusbar = new System.Windows.Forms.StatusStrip();
 			this.statuslabel = new System.Windows.Forms.ToolStripStatusLabel();
 			this.gridlabel = new System.Windows.Forms.ToolStripStatusLabel();
@@ -118,6 +119,7 @@ namespace CodeImp.DoomBuilder.Interface
 			this.linedefinfo = new CodeImp.DoomBuilder.Interface.LinedefInfoPanel();
 			this.redrawtimer = new System.Windows.Forms.Timer(this.components);
 			this.display = new CodeImp.DoomBuilder.Interface.RenderTargetControl();
+			this.itemautomerge = new System.Windows.Forms.ToolStripMenuItem();
 			toolStripMenuItem1 = new System.Windows.Forms.ToolStripSeparator();
 			toolStripMenuItem2 = new System.Windows.Forms.ToolStripSeparator();
 			toolStripMenuItem3 = new System.Windows.Forms.ToolStripSeparator();
@@ -174,7 +176,7 @@ namespace CodeImp.DoomBuilder.Interface
 			// toolStripSeparator6
 			// 
 			toolStripSeparator6.Name = "toolStripSeparator6";
-			toolStripSeparator6.Size = new System.Drawing.Size(158, 6);
+			toolStripSeparator6.Size = new System.Drawing.Size(162, 6);
 			// 
 			// toolStripSeparator3
 			// 
@@ -197,7 +199,7 @@ namespace CodeImp.DoomBuilder.Interface
 			// toolStripMenuItem5
 			// 
 			toolStripMenuItem5.Name = "toolStripMenuItem5";
-			toolStripMenuItem5.Size = new System.Drawing.Size(158, 6);
+			toolStripMenuItem5.Size = new System.Drawing.Size(162, 6);
 			// 
 			// toolStripSeparator10
 			// 
@@ -218,7 +220,7 @@ namespace CodeImp.DoomBuilder.Interface
 			// toolStripSeparator11
 			// 
 			toolStripSeparator11.Name = "toolStripSeparator11";
-			toolStripSeparator11.Size = new System.Drawing.Size(158, 6);
+			toolStripSeparator11.Size = new System.Drawing.Size(162, 6);
 			// 
 			// poscommalabel
 			// 
@@ -334,6 +336,7 @@ namespace CodeImp.DoomBuilder.Interface
             this.itemthingsmode,
             toolStripSeparator6,
             this.itemsnaptogrid,
+            this.itemautomerge,
             toolStripSeparator11,
             this.itemmapoptions});
 			this.menuedit.Name = "menuedit";
@@ -344,7 +347,7 @@ namespace CodeImp.DoomBuilder.Interface
 			// 
 			this.itemundo.Image = global::CodeImp.DoomBuilder.Properties.Resources.Undo;
 			this.itemundo.Name = "itemundo";
-			this.itemundo.Size = new System.Drawing.Size(161, 22);
+			this.itemundo.Size = new System.Drawing.Size(165, 22);
 			this.itemundo.Tag = "undo";
 			this.itemundo.Text = "Undo";
 			this.itemundo.Click += new System.EventHandler(this.InvokeTaggedAction);
@@ -353,7 +356,7 @@ namespace CodeImp.DoomBuilder.Interface
 			// 
 			this.itemredo.Image = global::CodeImp.DoomBuilder.Properties.Resources.Redo;
 			this.itemredo.Name = "itemredo";
-			this.itemredo.Size = new System.Drawing.Size(161, 22);
+			this.itemredo.Size = new System.Drawing.Size(165, 22);
 			this.itemredo.Tag = "redo";
 			this.itemredo.Text = "Redo";
 			this.itemredo.Click += new System.EventHandler(this.InvokeTaggedAction);
@@ -362,7 +365,7 @@ namespace CodeImp.DoomBuilder.Interface
 			// 
 			this.itemverticesmode.Image = global::CodeImp.DoomBuilder.Properties.Resources.VerticesMode;
 			this.itemverticesmode.Name = "itemverticesmode";
-			this.itemverticesmode.Size = new System.Drawing.Size(161, 22);
+			this.itemverticesmode.Size = new System.Drawing.Size(165, 22);
 			this.itemverticesmode.Tag = "verticesmode";
 			this.itemverticesmode.Text = "Vertices Mode";
 			this.itemverticesmode.Click += new System.EventHandler(this.InvokeTaggedAction);
@@ -371,7 +374,7 @@ namespace CodeImp.DoomBuilder.Interface
 			// 
 			this.itemlinedefsmode.Image = global::CodeImp.DoomBuilder.Properties.Resources.LinesMode;
 			this.itemlinedefsmode.Name = "itemlinedefsmode";
-			this.itemlinedefsmode.Size = new System.Drawing.Size(161, 22);
+			this.itemlinedefsmode.Size = new System.Drawing.Size(165, 22);
 			this.itemlinedefsmode.Tag = "linedefsmode";
 			this.itemlinedefsmode.Text = "Linedefs Mode";
 			this.itemlinedefsmode.Click += new System.EventHandler(this.InvokeTaggedAction);
@@ -380,7 +383,7 @@ namespace CodeImp.DoomBuilder.Interface
 			// 
 			this.itemsectorsmode.Image = global::CodeImp.DoomBuilder.Properties.Resources.SectorsMode;
 			this.itemsectorsmode.Name = "itemsectorsmode";
-			this.itemsectorsmode.Size = new System.Drawing.Size(161, 22);
+			this.itemsectorsmode.Size = new System.Drawing.Size(165, 22);
 			this.itemsectorsmode.Tag = "sectorsmode";
 			this.itemsectorsmode.Text = "Sectors Mode";
 			this.itemsectorsmode.Click += new System.EventHandler(this.InvokeTaggedAction);
@@ -389,7 +392,7 @@ namespace CodeImp.DoomBuilder.Interface
 			// 
 			this.itemthingsmode.Image = global::CodeImp.DoomBuilder.Properties.Resources.ThingsMode;
 			this.itemthingsmode.Name = "itemthingsmode";
-			this.itemthingsmode.Size = new System.Drawing.Size(161, 22);
+			this.itemthingsmode.Size = new System.Drawing.Size(165, 22);
 			this.itemthingsmode.Tag = "thingsmode";
 			this.itemthingsmode.Text = "Things Mode";
 			this.itemthingsmode.Click += new System.EventHandler(this.InvokeTaggedAction);
@@ -400,7 +403,7 @@ namespace CodeImp.DoomBuilder.Interface
 			this.itemsnaptogrid.CheckState = System.Windows.Forms.CheckState.Checked;
 			this.itemsnaptogrid.Image = global::CodeImp.DoomBuilder.Properties.Resources.Grid4;
 			this.itemsnaptogrid.Name = "itemsnaptogrid";
-			this.itemsnaptogrid.Size = new System.Drawing.Size(161, 22);
+			this.itemsnaptogrid.Size = new System.Drawing.Size(165, 22);
 			this.itemsnaptogrid.Tag = "togglesnap";
 			this.itemsnaptogrid.Text = "Snap to Grid";
 			this.itemsnaptogrid.Click += new System.EventHandler(this.InvokeTaggedAction);
@@ -409,7 +412,7 @@ namespace CodeImp.DoomBuilder.Interface
 			// 
 			this.itemmapoptions.Image = global::CodeImp.DoomBuilder.Properties.Resources.Properties;
 			this.itemmapoptions.Name = "itemmapoptions";
-			this.itemmapoptions.Size = new System.Drawing.Size(161, 22);
+			this.itemmapoptions.Size = new System.Drawing.Size(165, 22);
 			this.itemmapoptions.Tag = "mapoptions";
 			this.itemmapoptions.Text = "Map Options....";
 			this.itemmapoptions.Click += new System.EventHandler(this.InvokeTaggedAction);
@@ -485,7 +488,8 @@ namespace CodeImp.DoomBuilder.Interface
             this.buttonthingsfilter,
             this.thingfilters,
             this.toolStripSeparator8,
-            this.buttonsnaptogrid});
+            this.buttonsnaptogrid,
+            this.buttonautomerge});
 			this.toolbar.Location = new System.Drawing.Point(0, 24);
 			this.toolbar.Name = "toolbar";
 			this.toolbar.Size = new System.Drawing.Size(839, 25);
@@ -644,6 +648,19 @@ namespace CodeImp.DoomBuilder.Interface
 			this.buttonsnaptogrid.Text = "Snap to Grid";
 			this.buttonsnaptogrid.Click += new System.EventHandler(this.InvokeTaggedAction);
 			// 
+			// buttonautomerge
+			// 
+			this.buttonautomerge.Checked = true;
+			this.buttonautomerge.CheckState = System.Windows.Forms.CheckState.Checked;
+			this.buttonautomerge.DisplayStyle = System.Windows.Forms.ToolStripItemDisplayStyle.Image;
+			this.buttonautomerge.Image = global::CodeImp.DoomBuilder.Properties.Resources.mergegeometry2;
+			this.buttonautomerge.ImageTransparentColor = System.Drawing.Color.Magenta;
+			this.buttonautomerge.Name = "buttonautomerge";
+			this.buttonautomerge.Size = new System.Drawing.Size(23, 22);
+			this.buttonautomerge.Tag = "toggleautomerge";
+			this.buttonautomerge.Text = "Merge Geometry";
+			this.buttonautomerge.Click += new System.EventHandler(this.InvokeTaggedAction);
+			// 
 			// statusbar
 			// 
 			this.statusbar.Font = new System.Drawing.Font("Verdana", 8.25F, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, ((byte)(0)));
@@ -970,6 +987,17 @@ namespace CodeImp.DoomBuilder.Interface
 			this.display.Paint += new System.Windows.Forms.PaintEventHandler(this.display_Paint);
 			this.display.MouseUp += new System.Windows.Forms.MouseEventHandler(this.display_MouseUp);
 			// 
+			// itemautomerge
+			// 
+			this.itemautomerge.Checked = true;
+			this.itemautomerge.CheckState = System.Windows.Forms.CheckState.Checked;
+			this.itemautomerge.Image = global::CodeImp.DoomBuilder.Properties.Resources.mergegeometry2;
+			this.itemautomerge.Name = "itemautomerge";
+			this.itemautomerge.Size = new System.Drawing.Size(165, 22);
+			this.itemautomerge.Tag = "toggleautomerge";
+			this.itemautomerge.Text = "Merge Geometry";
+			this.itemautomerge.Click += new System.EventHandler(this.InvokeTaggedAction);
+			// 
 			// MainForm
 			// 
 			this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.None;
@@ -1080,5 +1108,7 @@ namespace CodeImp.DoomBuilder.Interface
 		private System.Windows.Forms.ToolStripButton buttonredo;
 		private System.Windows.Forms.ToolStripButton buttonsnaptogrid;
 		private System.Windows.Forms.ToolStripMenuItem itemsnaptogrid;
+		private System.Windows.Forms.ToolStripButton buttonautomerge;
+		private System.Windows.Forms.ToolStripMenuItem itemautomerge;
 	}
 }
\ No newline at end of file
diff --git a/Source/Interface/MainForm.cs b/Source/Interface/MainForm.cs
index 48e2654d..237f6b6c 100644
--- a/Source/Interface/MainForm.cs
+++ b/Source/Interface/MainForm.cs
@@ -77,6 +77,7 @@ namespace CodeImp.DoomBuilder.Interface
 		public bool MouseInDisplay { get { return mouseinside; } }
 		public RenderTargetControl Display { get { return display; } }
 		public bool SnapToGrid { get { return buttonsnaptogrid.Checked; } }
+		public bool AutoMerge { get { return buttonautomerge.Checked; } }
 
 		#endregion
 
@@ -872,14 +873,15 @@ namespace CodeImp.DoomBuilder.Interface
 			//menuedit.Visible = (General.Map != null);
 			
 			// Enable/disable items
+			itemundo.Enabled = (General.Map != null) && (General.Map.UndoRedo.NextUndo != null);
+			itemredo.Enabled = (General.Map != null) && (General.Map.UndoRedo.NextRedo != null);
 			itemmapoptions.Enabled = (General.Map != null);
 			itemverticesmode.Enabled = (General.Map != null);
 			itemlinedefsmode.Enabled = (General.Map != null);
 			itemsectorsmode.Enabled = (General.Map != null);
 			itemthingsmode.Enabled = (General.Map != null);
 			itemsnaptogrid.Enabled = (General.Map != null);
-			itemundo.Enabled = (General.Map != null) && (General.Map.UndoRedo.NextUndo != null);
-			itemredo.Enabled = (General.Map != null) && (General.Map.UndoRedo.NextRedo != null);
+			itemautomerge.Enabled = (General.Map != null);
 
 			// Determine undo description
 			if(itemundo.Enabled)
@@ -904,6 +906,7 @@ namespace CodeImp.DoomBuilder.Interface
 			buttonundo.ToolTipText = itemundo.Text;
 			buttonredo.ToolTipText = itemredo.Text;
 			buttonsnaptogrid.Enabled = (General.Map != null);
+			buttonautomerge.Enabled = (General.Map != null);
 		}
 
 		// Action to toggle snap to grid
@@ -913,6 +916,14 @@ namespace CodeImp.DoomBuilder.Interface
 			buttonsnaptogrid.Checked = !buttonsnaptogrid.Checked;
 			itemsnaptogrid.Checked = buttonsnaptogrid.Checked;
 		}
+
+		// Action to toggle auto merge
+		[Action("toggleautomerge")]
+		public void ToggleAutoMerge()
+		{
+			buttonautomerge.Checked = !buttonautomerge.Checked;
+			itemautomerge.Checked = buttonautomerge.Checked;
+		}
 		
 		#endregion
 
diff --git a/Source/Map/Linedef.cs b/Source/Map/Linedef.cs
index 575ca310..9fe26974 100644
--- a/Source/Map/Linedef.cs
+++ b/Source/Map/Linedef.cs
@@ -75,9 +75,6 @@ namespace CodeImp.DoomBuilder.Map
 		
 		// Selections
 		private bool selected;
-
-		// Cloning
-		private Linedef clone;
 		
 		// Disposing
 		private bool isdisposed = false;
diff --git a/Source/Properties/Resources.Designer.cs b/Source/Properties/Resources.Designer.cs
index 33126dd3..fdb932a7 100644
--- a/Source/Properties/Resources.Designer.cs
+++ b/Source/Properties/Resources.Designer.cs
@@ -109,6 +109,20 @@ namespace CodeImp.DoomBuilder.Properties {
             }
         }
         
+        internal static System.Drawing.Bitmap mergegeometry {
+            get {
+                object obj = ResourceManager.GetObject("mergegeometry", resourceCulture);
+                return ((System.Drawing.Bitmap)(obj));
+            }
+        }
+        
+        internal static System.Drawing.Bitmap mergegeometry2 {
+            get {
+                object obj = ResourceManager.GetObject("mergegeometry2", resourceCulture);
+                return ((System.Drawing.Bitmap)(obj));
+            }
+        }
+        
         internal static System.Drawing.Bitmap NewMap {
             get {
                 object obj = ResourceManager.GetObject("NewMap", resourceCulture);
diff --git a/Source/Properties/Resources.resx b/Source/Properties/Resources.resx
index 5a9296ed..bc03f1bc 100644
--- a/Source/Properties/Resources.resx
+++ b/Source/Properties/Resources.resx
@@ -145,6 +145,9 @@
   <data name="NewMap" type="System.Resources.ResXFileRef, System.Windows.Forms">
     <value>..\Resources\NewMap2.png;System.Drawing.Bitmap, System.Drawing, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a</value>
   </data>
+  <data name="mergegeometry" type="System.Resources.ResXFileRef, System.Windows.Forms">
+    <value>..\Resources\mergegeometry.png;System.Drawing.Bitmap, System.Drawing, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a</value>
+  </data>
   <data name="File" type="System.Resources.ResXFileRef, System.Windows.Forms">
     <value>..\Resources\NewMap.png;System.Drawing.Bitmap, System.Drawing, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a</value>
   </data>
@@ -163,8 +166,8 @@
   <data name="Grid2" type="System.Resources.ResXFileRef, System.Windows.Forms">
     <value>..\Resources\Grid2.png;System.Drawing.Bitmap, System.Drawing, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a</value>
   </data>
-  <data name="ThingsMode" type="System.Resources.ResXFileRef, System.Windows.Forms">
-    <value>..\Resources\ThingsMode.png;System.Drawing.Bitmap, System.Drawing, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a</value>
+  <data name="Grid4" type="System.Resources.ResXFileRef, System.Windows.Forms">
+    <value>..\Resources\Grid4.png;System.Drawing.Bitmap, System.Drawing, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a</value>
   </data>
   <data name="SaveMap" type="System.Resources.ResXFileRef, System.Windows.Forms">
     <value>..\Resources\SaveMap.png;System.Drawing.Bitmap, System.Drawing, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a</value>
@@ -175,6 +178,9 @@
   <data name="VerticesMode" type="System.Resources.ResXFileRef, System.Windows.Forms">
     <value>..\Resources\VerticesMode.png;System.Drawing.Bitmap, System.Drawing, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a</value>
   </data>
+  <data name="ThingsMode" type="System.Resources.ResXFileRef, System.Windows.Forms">
+    <value>..\Resources\ThingsMode.png;System.Drawing.Bitmap, System.Drawing, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a</value>
+  </data>
   <data name="Status1" type="System.Resources.ResXFileRef, System.Windows.Forms">
     <value>..\Resources\Status1.png;System.Drawing.Bitmap, System.Drawing, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a</value>
   </data>
@@ -184,7 +190,7 @@
   <data name="OpenMap" type="System.Resources.ResXFileRef, System.Windows.Forms">
     <value>..\Resources\OpenMap.png;System.Drawing.Bitmap, System.Drawing, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a</value>
   </data>
-  <data name="Grid4" type="System.Resources.ResXFileRef, System.Windows.Forms">
-    <value>..\Resources\Grid4.png;System.Drawing.Bitmap, System.Drawing, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a</value>
+  <data name="mergegeometry2" type="System.Resources.ResXFileRef, System.Windows.Forms">
+    <value>..\Resources\mergegeometry2.png;System.Drawing.Bitmap, System.Drawing, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a</value>
   </data>
 </root>
\ No newline at end of file
diff --git a/Source/Resources/Actions.cfg b/Source/Resources/Actions.cfg
index dcec5cc7..a446d997 100644
--- a/Source/Resources/Actions.cfg
+++ b/Source/Resources/Actions.cfg
@@ -208,8 +208,8 @@ gridsetup
 	title = "View: Grid Setup";
 	description = "Shows the Custom Grid Setup dialog which allows you to set custom grid sizes and a background image.";
 	allowkeys = true;
-	allowmouse = false;
-	allowscroll = false;
+	allowmouse = true;
+	allowscroll = true;
 }
 
 undo
@@ -217,8 +217,8 @@ undo
 	title = "Edit: Undo";
 	description = "Restores the current map as it was before last action(s) performed.";
 	allowkeys = true;
-	allowmouse = false;
-	allowscroll = false;
+	allowmouse = true;
+	allowscroll = true;
 }
 
 redo
@@ -226,8 +226,8 @@ redo
 	title = "Edit: Redo";
 	description = "Repeates the action(s) performed before Undo was used.";
 	allowkeys = true;
-	allowmouse = false;
-	allowscroll = false;
+	allowmouse = true;
+	allowscroll = true;
 }
 
 togglesnap
@@ -235,6 +235,15 @@ togglesnap
 	title = "Edit: Snap to Grid";
 	description = "Toggles snapping to the grid for things and vertices that are being dragged.";
 	allowkeys = true;
+	allowmouse = false;
+	allowscroll = false;
+}
+
+toggleautomerge
+{
+	title = "Edit: Merge Geometry";
+	description = "Toggles automatic merging of geometry for vertices and structures that are being dragged.";
+	allowkeys = true;
 	allowmouse = true;
 	allowscroll = true;
 }
diff --git a/Source/Resources/mergegeometry.png b/Source/Resources/mergegeometry.png
new file mode 100644
index 00000000..c9c44274
Binary files /dev/null and b/Source/Resources/mergegeometry.png differ
diff --git a/Source/Resources/mergegeometry2.png b/Source/Resources/mergegeometry2.png
new file mode 100644
index 00000000..f8af3f15
Binary files /dev/null and b/Source/Resources/mergegeometry2.png differ