When you have selected a SWITCH entity, use the [>] key to zoom closer to the wall you wish to mount your switch to, and you will notice the arrow. Make sure the arrow is very close to the segment wall, and then click the LEFT MOUSE BUTTON to attach a copy of the switch to the wall. Then RIGHT MOUSE BUTTON to end the selection, and right mouse button again ON the new switch entity. If the first attempt failed, you can use the [I] key when editing an entity to allow it to find a wall. Remember the entity needs to be 75 units or less distance from the wall!
"We are the knights who say...eki eki eki fatang loopzoing, zanziga....ni"