Spider-man Walls

Ladders can be climbed on from the outside if placed clipping into sheet metal walls.

Tutorial
Move your mouse up until the ladder is clipping into the cross bars of the soft side sheet metal wall. The height of the ladder depends on how high the spider-man wall will be. For two walls high the ladder should go near the top at the height demonstrated by the picture. Confirm the placement by testing on the other side.

Credit
Tommy