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The accurate installation of all carpentry trim on a project is a matter of adhering to a basic mathematical process for defining angles for precise cutting of mitered joints and connections. Understanding the method will ensure that the joining of any two pieces of trim will be matched perfectly and provide professional results throughout the project. Follow these steps to correctly measure the angles for carpentry trim work.
Set a bevel square against the two adjacent surface planes to be trimmed and tighten the square's set screw to lock the angle.
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Place the bevel square's handle side against the base of a protractor and read the protractor's degree scale to define the angle.
Divide by 2 the angle determined in Step 2. Example: a 60-degree angle divided by 2 results in two 30-degree angles and a 90-degree angle divided by 2 results in two 45-degree angles. This formula is used to calculate any angle required.
Set the miter saw to the angle determined in Step 3 and cut the two pieces of trim to be joined together.
Position one of the trim pieces cut in Step 4 in place with the short side of the angled cut flush with the corner being trimmed. Position the second piece of trim on the adjacent side to check that the two pieces match and nail both pieces in place.