Whoever fitted the boiler in our back room also left a hole that goes all the way from inside to outside. I’ve been meaning to block it up since we moved in half a decade ago but now that I have a 3D printer, there seemed no excuse to put it off further. You can see the exposed grey plug of my design just past the drip pipe.

Inside the hole is a small riser to grip it by, topped by four slightly splayed wings. The idea is that the plug is wider than the hole, the riser fits inside comfortably and the wings need a little bend to push the piece inside. I’ve published the piece on MakerWorld, including the .scad design file that will allow others to customise to fit their needs. I’ve also printed a couple off myself – the one you see and another one for the hole on the inside.