There are as many base feet in a valley rafter as there are number of feet in 1/2 the width of the gable. (Fig. 21.) To obtain the length of a valley rafter, lay the square on the rafter at 17" base and the rise of the common rafter, as many successive times as there are base feet to be spanned. (Fig. 37.) Mark on the base for the plate cut and on the rise for the perpendicular cut to meet the ridge.

The angular cut, to meet the ridge, is the same rule given for the hip rafter. (Fig. 40.) Mark 3/8" lower than the base mark for the base cut to raise the center of the rafter to line with common rafters. (See fig. 42.)