My library has recently purchased new 5-drawer map cases that are perfectly flat on the bottom and top, and the movers noticed while they were stacking them that the cases do slide where the bottom of one case sits on the top of another. We will be stacking them 3 cases high. Will the cases be stable when the drawers are full or is this a safety problem? What do others do? I did not find in the listserv archives a discussing of anchoring or attaching cases to each other or the wall.