How to Cap Window Trim With Aluminum

Set the aluminum drip cap on top of the window's header trim with the front tab pressed against the trim. Slide the drip cap down until the right end extends just 1/2 inch past the header trim's right end. Mark the drip cap's left end 1/2 inch past the header trim's left end.

Cut the aluminum drip cap with a tin snips along the mark you made on the left-hand side. Cut the tab and back edge first, then bend the drip cap and cut the bottom edge. Center the drip cap back over the header trim, with 1/2 inch extending past on both ends.

Mark the tab on both ends where it meets the side trim pieces. Cut off this small piece of tab with a tin snips on both ends. Cut the corner where the bottom edge meets the back edge the same distance in as the piece of tab you removed.

Bend one of the bottom edges ends down. Set the aluminum drip cap back on the trim header and slide it down until the bent end presses against the side trim. Bend the bottom edge's other end down against the side trim.

Hammer three 1 1/4-inch nails through the back edge. Position the one nail about 2 inches in from both ends and another nail centered between the first two.