Side Cut Of Octagonal And Other Polygonal Jacks. First Method: The method described in Section 35 is applicable to jacks as well.
Second Method: If a table of common rafter lengths per foot of run is available, the side cut of any polygonal jack may be laid out by placing the framing square across the top of the rafter, taking the tangent value of the polygon on the tongue, and the length of common rafter per foot of run on the blade, and scribing on the blade. The tangent of the polygon forms the opposite side of a triangle in which the adjacent side is the length of common or jack rafter per foot of run. The angle formed being the angle of side cut of jack.