I have some utility shelves I built to store those large plastic storage bins. I'd like to make doors for each shelf level that are hinged at the bottom and run the width of each shelf. The idea is that when the door is open I could pull out the bins and the door would support them while I sort through the useless junk I've got stored away in them.

Is there a heavy-duty bracket for this purpose? I visualize one at each end of each door, sort of like a drop-down desktop bracket on steroids. They would have to support say 50 lbs.

 

Try Rockler's. Trunk, Chest and Case Hardware ? Locks, Latches, Lid Supports, Hinges ? Rockler

 

Depending on how much you want to spend on hardware you may just want to use some chain attached by threaded eye hooks for each end of your shelf. The photo in the attached link shows both a polished brass lid support as well as a chain installed as a safety chain. For what you described I think a pair of chains would more than satisfy the need.