Well, well, well. I've heard of French cleats. Yes sir, these are a type of French cleats. I thought it was something the Paris football team wore.
John, I'm with you on using screws, it's a much stronger, more secure way to hang things. But my wife likes to rearrange things and this is easier for her and me. Happy wife = happy life.
I bet these would be easy to make on a 3D printer. Hint, hint.
BTW, I can't seem to stop making these birdhouses. Am I sick? (Don't answer that Jerry.) it's a great use of scraps, which I have plenty of.