Interior window trim helps to hide gaps between the window frame and the wall, and can add any type of look you want. The apron is the portion under the window that pulls all the trim together. Installing this is simple with the right tools and materials.
Step 1 - Measure and Cut
Start by measuring the area you are placing the apron. You want to make sure you get the distance between the legs where they will contact the sill. With this number you can cut a piece of apron to the appropriate length.
Step 2 - Prepare the Apron
You want to cut a beveled edge on both ends of the apron at a 45 degree angle.
Step 3 - Installation
Press the apron against the window sill until it lines up properly. Many people use an adhesive to hold it in place, but this isn't necessary. You can choose to install this with a glue or use finishing nails.
Step 4 - Check for Level
Go back behind yourself and make sure everything lines up. If it doesn't it's easier to correct before the adhesive dries, or before you cover the finishing nail holes.