A quick learner says:
October 8, 2016
these brackets hold the pivot pins and hold the mirror to the frame on a bi-fold mirror door, not a good design due to the weight of the door as you can see this one broke so I expect them all to break
Paul from SWISCO responded:
October 11, 2016
Our 23-409 corner connector looks like a close match for what you're looking for. See what you think.