This end cap is universal, fits both left and right gutter ends. With the EPDM rubber gasket (same type of rubber that seals cars or truck doors) and the 4 flanges specifically developed to grip and seal, this is as easy as it gets. Simply align it over the bead and the backside of the gutter, slap it on with your hand or a rubber mallet. You can fold off the ear against the fascia if you have to. No caulking, crimping, rivets or screws to hold it in place. The EPDM seals and grips on tight, and you will have zero leaks.