Common Rafter For Plate Of Any Number Of Sides. By referring to Figs. 68 and 72 it will be seen that common rafters have for their runs the apothem of the polygon made by the plate, represented in Fig. 68 by the lines b, b', b". The run of the hip is represented by the line c, c', c". The rise will be found the same for full length common rafters and hips. Plumb and seat cuts and lengths per foot of run of common rafters and jacks are determined for a building of any number of sides just as for the square cornered building. The degree of inclination of common and jack rafter is applicable, too, Fig. 49.