Quick Method to Calculate ⅔ Height Above Plate (HAP) for Birdsmouth Cuts ✂️

There are two schools of thought for cutting a birdsmouth: fully seated cuts and two-thirds cuts.

And depending on which one you use, you can get two different “height above plate” measures. This is how you calculate a ⅔ HAP using a Construction Master Pro 👇

1️⃣ Enter the rafter’s pitch
2️⃣ Enter the rafter’s width (for a 2x8 that’s 7.25 inches) and push RUN
3️⃣ Push Diag for the hypotenuse
4️⃣ Multiply the Diag by 2, then divide by 3 to account for how much you’ll lower the rafter when you cut the birdsmouth
5️⃣ Push INCH if you want to convert to fractional inches

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