Hinges.
measure and mask off the lines I want to cut, out of 1.5" x 1.5" angle thats 1/8" thick.
Here are the 2 male ends that are attached to the physical tonneau its self. Just cut out not trimmed or clean, so they look rough.
Here are the 2 finished products. How they work on the left and separate on the right. I then glued the male ends to the tonneau, drilled counter sunk, and screwed them to the tonneau. Because this is a high stress point of the tonneau (hinge) I felt threaded screws would help hold it to the tonneau better then an aluminum rivit.