Tiny under-shelf mount picture frame corners

My desk has several shelves above it, and I wanted a way to hang pictures vertically underneath. These are tiny, simple little pieces that let you hang pictures, artwork, etc. of almost any size on the underside of shelves, desks, cabinets, etc. Just add a piece of double-stick tape to the flat part, push a thumbtack through the holes, and viola. It probably won't hold a lot of weight, but it should hold pictures or paper artwork just fine.