How to Frame Around a Bathroom Window

Measure along the top of the window opening, from one top corner to the other at the edge, using a measuring tape.

Transfer the measurement to a piece of trim with two pencil marks on the bottom edge of the trim.

Set the trim on a miter saw, face up, with the bottom edge against the back rail of the saw. Slide the trim to put one of the marks in front of the blade. Swivel the blade to point 45 degrees outward, away from middle of the trim. Make the cut.

Slide the trim so the second mark is under the blade. Swivel the blade in the opposite direction from before so it again points 45 degrees outward. Make the cut.

Set the trim along the upper edge of the window opening so the bottom of the piece lines up with the top edge and the cut ends angle up and off each top corner. Use your hammer and trim nails to secure it, placing a nail every foot along the upper and lower edges of the trim.

Repeat the process for each of the other sides of the window, measuring and cutting the trim and nailing it in place. The mitered ends of the trim should butt to one another to form the corners.