Fig. 72. Run of Common.
Rafter of any Roof is
Apothem of Polygon sidered as 13". To lay off a plumb cut for an octagonal hip or valley, take 13" on the tongue and the rise per foot of run of common rafter on the blade, Fig. 73; scribe on the blade.
In a similar manner, having determined the tangent of any polygon under consideration, the run of hip or valley per foot of run of common rafter may be figured. The result will give the number to take on the tongue when the rise per foot of run of common rafter is taken on the blade, for laying out plumb cuts.
Fig. 73. Table for Octagon Hip or Valley.