Simple mount for a single relay I'm using with an Arduino. Possibly others like it are better but I couldn't find one so simply created one in TinkerCad and printed it. I suspect there are many versions of this relay board so it may not fit exactly one you might have. It fits the boards I have just fine. I may heat stake the posts to hold the board firmly. I added three screw holes, for 3mm hardware, but intend on using the one on the tab at the top. No special print settings.