I must confess that I have only been involved with these in actual use on a couple of vehicles (-seen them on many, just not been involved with a couple) however the issue I saw in both examples was you could not have placed the stuff inside both of those tool boxes any better with a dump truck.
As I recall, neither driver could locate what they thought they had inside. Since both of these were not being used as a tool box but more of a catch all, my question to others is just exactly what do you carry in these that is such a necessity to have?