How to Trim a Window Casing Apron

Window trim is applied to the interior of a window to cover the gap between the wall and the window. Trim style can range from a basic, narrow piece of trim to more ornate, multiple-piece moldings. Regardless of the complexity or style, the terminology is the same. The upper horizontal piece is called the header, the vertical pieces are the legs and the lower horizontal piece is the apron. The window sill, also called the stool cap, is a piece of trim that protrudes from the wall beyond the face of the trim and separates the legs from the apron. Installing apron trim is perhaps the easiest part of trimming the window.

Tape measure
Casing
Saw
Hammer
Finish nails
Glue
Tape

Instructions

- 1
  Measure the distance between the outside of the legs where they touch the window sill to determine the length of the apron.
- 2
  Cut the apron out of a piece of window casing using this measurement.
- 3
  Cut a 45-degree bevel on both ends of the apron.
- 4
  Install the apron under the window sill. Press the apron firmly against the sill and line the ends up with the outsides of the legs. Nail the apron into the wall studs.
- 5
  Cut return pieces that will fit into the beveled ends of the apron. Cut the left-hand return, making a straight cut and then a 45-degree right bevel. The cuts will meet together at the back of the casing. Reverse the order to make the right return piece.
- 6
  Apply glue to the beveled edges of the apron and install the returns. Tape the returns in place until the glue dries.

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