The hinges are made from 5/32" x 2" aluminum tubing and a robart pin hinge. The hinge is slid into the tubing and then the tubing is crimped. For the two hinges on the inboard sides of the elevator, I wanted more strength there so I used the larger robart hinges set into 7/32" x 2" tubing. Here is a couple of pics showing them temporarily installed in the elevators.