Pictureframe keyhole hanger insert

thingiverse

This keyhole hanger can be slid into a hole to display pictures or lightweight pieces of furniture. Depending on the drill bit and the softness of the wood, you may need to enlarge the hanger slightly (e.g., 20.2 mm for a 20 mm hole). For particularly critical items, consider adding a drop of epoxy to one side before inserting it into the hole.