STLs of the five platonic solids as cabinet doorknobs. As suggested by Matt Parker during the most recent episode of A Problem Squared, which is magnificent. Come with an M6 hex bolt drop-in slot. Simply drop in a bolt with a length of (30 + T)mm, head first, where T is the thickness of the surface you're mounting the bolt through. Fastening the nut on the other side should lock the bolt in place through an internal design I'm frankly disproportionately proud of. Approximately 35mm in diameter when printed at standard size. If anyone suggests they look somehow unsavory, I recommend smugly scorning them for not sufficiently appreciating polyhedra. Note that the icosahedron and tetrahedron will require some support while printing.