I have no idea how this would function as a doorknob but I love that you saw that.

My current out-of-bounds item list:

• Fidget and other sensory toys because I feel like moving in a certain way purely for the sake of itself isn’t in the spirit of these challenges.
• objects that are mostly or entirely ornamental / decorative in nature like jewelry and sculptures. I’ll still use something that is an ornamental version of something that has a specific non-ornamental purpose (ex: a lot of traditional fibercraft tools or recreational drug equipment for weed or caffeine). Hair ornaments and pins are fine as long as they have some specific niche use such as ornamental hair rollers or having an interesting closure for pinning your shawl in a specific way or something.
• tools that are too broadly applicable such as specialty abrasive drill bits or specialty brushes where what makes them use specific is stuff like size shape and bristle stiffness which are still pretty broadly applicable (a little brush with a long handle has a looot of different uses, think about everything you can do with a used toothbrush).
• Alternative “wellness” products that largely function as placebos by being in the general vicinity of a person such as crystals and “energy focusing copper coils” and the like. Weird looking traditional instruments like a special type of gong or something are acceptable.
• Specialty massage products are fine provided they’re mostly used to massage an area other than the genitals. It’s also still ok if the specific massage philosophy claims to have other, pseudo-scientific benefits such as for chiropracty or acupuncture, as long as the tool itself is an actual massage tool.