This fun little attachment changes one of your lens caps to a door peephole attachment. I put it on a 58mm cap as that’s what my video camera uses. All you need is some glue (I used dollar store 5 minute epoxy, my go-to) and a drill bit. I used a ½” or 13mm drill bit which was a bit loose but since drilling a hole dead center in a circle is hard, I found it easier to line it up on the lens cap after applying some glue. I also added glue along the length of the peep shaft and to the underside of the flange which is recessed into the print.

This is actually an improvement to a design I made years ago, by just drilling a hole in the lens cap and affixing the peephole to it. Unfortunately it was slightly off-center and didn't work as well as I would have liked.