With this mode you can edit the linedefs in your map. Every linedef has a front (right) and back (left) side which make up the boundaries of your sectors. You can edit the sidedef properties through the linedefs in this mode. Drag the linedefs to move them and snap them to the grid and other geometry. Hold Shift and/or Control to disable snapping to the grid and geometry.
The linedefs editing mode is one of the classic (2D) editing modes.
| L | Switches from any other classic editing mode to this mode. |
| Insert | Starts the Draw Geometry Mode. |
| Delete | Deletes the selected linedefs. Note that this may break your sectors. |
| F | Flips the linedef and changes the sidedefs so that they remain in their correct position. |
| Shift+F | Flips the sidedefs to the other side of the linedef. |
| Shift+S | Splits the linedef with a new vertex on the linedef, nearest to your mouse position. |
| Shift+1 | Keeps only the single-sided linedefs selected. |
| Shift+2 | Keeps only the double-sided linedefs selected. |
| Shift+C | Starts the Curve Linedefs Mode to make curves with the selected or highlighted linedefs. |