How to Determine Angles for Installing Molding

Wood molding is used to conceal joints and unfinished edges and as an ornamental framework around doors, windows and other wall features. An essential part of installing wood molding is accurately cutting mitered angles where the pieces intersect at two converging surface planes. The method of determining the correct miter cut angle is a simple mathematic formula that will define the overall angle and the miter saw settings for correct molding cuts.

Angle protractor
Adjustable bevel square

Instructions

- 1
  Position an adjustable bevel square at the converging angles to be defined. Hold the bevel square perpendicular to the wall planes. Press the side of the bevel square's handle against one plane and its blade edge against the adjacent plane. Lock the angle of the bevel square by tightening the set screw.
- 2
  Define the angle of the set bevel square using a protractor. Align the pivot point of the bevel square with the origin point on the protractor, with the bevel square's handle against the protractor's base. The point where the blade edge crosses the protractor's scale defines the angle in degrees.
- 3
  Calculate the molding's cut angle by dividing the bevel square angle by 2. For example: If a bevel square setting is determined to be 30 degrees, the miter saw cut angle for the molding would be 15 degrees for that corner.

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