Micro picture hanger

The first thing I designed after me moved to a new house and I bought a 3D printer. We needed to hang a bunch of pictures to decorate walls and a few reusable TODO lists for kids so they can write their tasks and put a checkmark when they are done. Therefore I needed a hanger that doesn't allow a frame to move while it's being written on. I also wanted something with as low profile as possible. And last but not least - something that will not leave the mess behind if we want to remove it.
That's how I came up with this tiny hanger. 7 month in and these little hangers still hold all the checklists (and pictures) very well.
Just print 2 of each, mount frame parts to the frame using a #4 wood screw and wall parts to the wall using some common picture hanging nails.