To replace a metal window trim, bend the strips to fit the window, measure the frame, cut and trim the flashing and then caulk the trim in place. The window frame must be completely clean before installing the trim.
To bend the strips, measure the metal to ensure it covers all areas of the frame, and then bend the metal with a vice. Next, measure the outside dimensions of the frame, and keep in mind that the lengths differ from inside to outside. If necessary, cut the strips down, but measure twice before cutting to ensure accuracy.
Cut the metal flashing so that it covers the entire wooden frame, and then use a pair of tin snips to remove any excess. Repeat this step for the bottom part of the window, and ensure all sides have coverage. Clean the window frame and sill with a brush and soapy water, and if there are any cracks, fill them using a putty knife with putty. Sand any areas of wood that are not level with the window frame.
If there are gaps between the building and window trim, fill this with caulking. Bend the metal as much as necessary to fit it into place, and then apply the caulking around it in beads. To finish the installation, with a damp finger, smooth the bead so it is smooth and level with the building and trim.