This gutter end cap is the fitting that attaches to and closes off the end of the gutter. It can be crimped, riveted, or screwed in place before applying sealant at the joint on the inside between the cap and trough seams. The flanged edges will cover a small amount of un eveness or rough cuts on the end of the trough. If riveting you will need to have a drill, drill bit, rivet gun, and rivets which are not included in this sale. Each Cap is marked L and R.