Simply cut at a 45 degree angle from bottom left to top right of the mitre box. The piece of coving to the left hand side of the saw blade can be discarded.
Are miter boxes accurate?
Precise: A power miter saw can lose its alignment with the material, especially when the tool is first activated. Manual miter boxes and backsaws can cut with greater precision, making them especially good for fine craftwork, such as creating picture frames.
