A slide-on clip that prevents wooden scissor-style dryer racks from collapsing unexpectedly.
Any. I used 3 layers per mm.
I made this with ABS, but any material will do. It doesn't carry any great stress, just keeping the rail of the rack from jumping out of a slot.
Print it on its side (so the hole is not vertical) with support for best strength.
Its possible that your rack will have a different size piece of wood, so print a small piece and check/adjust before printing the whole thing. Mine is just a hair under 10mm by 20mm. Takes about 30 minutes on my machine with a raft.
Remove the support material and sand down any sharp edges.