US Patent 9429424 Angular measurement tool

A right angle square includes a right isosceles triangle shaped right angle square with three sides. The three sides comprise a pitch edge, a hypotenuse, and another side. The right angle square also has a closed and arced angular measurement tube extending along a portion of a circumferential arc between the non-hypotenuse sides and the tube contains a fluid and a bubble that moved through the fluid. The right angle square also has a measurement scale. When the pitch edge is aligned against a slope to be measured, the bubble rises to the highest point in the tube, and the bubble is aligned on the measurement scale at a point along the measurement scale corresponding to the slope being measured.