Snap Walls 90°

The Snap Walls 90° command is found on the Edit menu.  Walls snap to an angle of 45° increments when this setting is turned on (check mark is displayed.)  When this toggle option is turned on walls will snap to 90° when dragged within a few degrees of vertical or horizontal.  This command also applies to floors and area dimensions.

Note:  There is a tolerance factor that applies to walls based on length, so if you try to drag a very long wall to a 90° angle when you are zoomed way out, the Snap Walls 90° command may not work as expected.  To address this, zoom in closer to the end being rotated.