While I like Mark's devices, the security screws are not particularly secure to anyone with a set of Allen wrenches, so I was interested in finding a padlock that could work in both the top and bottom locks and ideally be keyed the same. The 3/4 inch masterlock that Mark offers works for the top lock but does not work for the bottom lock. (I have one from a different source which I measured at 3/4", so I could be wrong there...) Searching for locks based on their dimensions is a lot harder than you'd think it would be, so if anyone has already found one that works or is a master at finding things, I'd appreciate them sharing.