The purpose of door and window trim is to hide the gap between the door and the window casing and between a window frame and the studs in the wall. There really are no differences in installation method between the two types of molding. You can even use the same trim profile to trim your windows and doors. The trim can be nailed into place with a hammer, but it is much easier and typically neater to use a pneumatic nailer to install trim.
Instructions
1. Measure from the floor for a door casing or from the sill for a window casing to both top corners of the door or window frame with a tape measure. Measure the width of the top edge of the door or window casing as well.
2. Cut three pieces of trim molding to the measurements taken in Step 1. Use a miter saw to make 45-degree cuts at the corners, using your measurements to mark the inside, or short end, of each 45-degree cut.
3. Use a block plane to shave the back sides of the mitered cuts off a little so the front sides of the molding will fit together tightly.
4. Hold one of the side pieces of molding up to the window or door frame, allow 3/16-inch of window or door casing to show and nail the trim into place with a pneumatic brad or finish nailer.
5. glue to the mitered edge of the piece of top trim and put it in its place above the door or window. Fit the mitered corner together and nail the glued side into place.
6. to the mitered cut on the last piece of trim and place the trim where it belongs on the other side of the door or window. Fit the mitered edges together and nail that side of the top piece of trim into place, followed by the side trim piece.
Tags: door window, into place, window casing, Apply wood, Apply wood glue