I originally saw these frames when I was browsing through LTD Commodities for Christmas gifts. They are a shadow box frame that has a pre-cut mat inside the frame. It has springs to push the artwork up against the mat, and opens from the front so you don't have to pull the frame off the wall each time you want to change the artwork. Each frame can hold about 50 flat art pieces. I bought one for my nephew for Christmas for $10 and thought they were the coolest things!
After she talked to me about it, I went onto Amazon and tried to find different sized frames. I found a set of three frames there for $100 and of a little better quality, so my principal ordered two sets!
These frames are SOOOOO nice! The hanging clips on the back are equally spaced out for vertical or horizontal hanging, so if I need to rotate the frames, I can do it without needing the custodians to rehang them!