I had a carbon monoxide detector that I needed to hang. I could have taken the simple route and pounded a couple of nails into the wall but I thought it might be fun to complicate things.
Actually, I just didn't want holes in my wall.
I got myself a variety pack of 3M Command strips. This hanger is designed to neatly cover the adhesive portion of a small Command strip - about 16mm x 23mm.
Don't expect this to hold much weight! The carbon monoxide detector is quite light and hangs on two of these things so they are overkill for the purpose. That said, if you try to hang a picture on one, you are liable not only to pull the hanger off the adhesive strip but to break the post of the hanger as well.
Given you want good adhesion with the strip, you will want a very smooth back. Print directly on glass (perhaps with glue stick if you don't have a heated bed) and clean with rubbing alcohol both on the mount and the wall to ensure no grease is there to thwart adhesion.
This should be an extremely simple print overall. No supports are required! Make sure you have adequate part cooling near the top or just dial back your speed to ensure the post cools adequately as it is printed, instead of getting knocked around by the hot end.
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