This thing holds a campervan ladder which is attached to some hooks on top. I used some velcro before. The holms are 40mm x 18mm with rounded edges and sides.
The first version (08 09) works, but I found that due to the special place at my campervan, I can't get the ladder far enough from the wall. The 08 is 20mm wide, but is very stiff. I added a 12mm version (09). The pins next to the hole are used against rotation.
The second version (14) is used to put the ladder in from the side.
I added two versions with slightly thicker material (16 and 16a). They still flex OK, but might hold better.