Casing Trim Cutting Tips and Tricks

This instructable describes one geometric method of installing door and window casing

Mark the door corners where the casing will meet and then mark the height on the vertical casing.

Cut 45 degrees at the marks on the vertical casing pieces

Cut a 45 on one side of the top piece then hold up to the vertical miter to see if the angle needs to be modified.

Slightly adjust the saw and recut the miter of the top piece so that the miter is perfect.

Cut a 45 on the top casing for the opposite side, but don't cut to length. Also make an adjustment until the angle is correct. Leave the saw at that angle.

With the saw at the correct angle, cut the top piece to length.

Dry fit the miter.

Nail in place