By making the drawings large, as we have already suggested and insisted upon, we can secure an accuracy closely approximating perfection. As, for instance, if we wish to get a lock of one and a half degrees on the locking face of the entrance pallet E, we measure down on the arc c'' from its intersection with the peripheral line m one and a half degrees, and establish the point r and thus locate the outer angle of the entrance pallet E, so there will really be one and a half degrees of lock; and by measuring down on the arc d' ten degrees from its intersection with the peripheral line m, we locate the point s, which determines the position of the inner angle of the entrance pallet, and we know for a certainty that when this inner angle is freed from the tooth it will be after the pallet (and, of course, the lever) has passed through exactly ten degrees of angular motion.

For locating the inner angle of the exit pallet, we measure on the arc d', from its intersection with the peripheral line m, eight and a half degrees, and establish the point n, which locates the position of this inner angle; and, of course, one and a half degrees added on the arc d' indicates the extent of the lock on this pallet. Such drawings not only enable us to theorize to extreme exactness, but also give us proportionate measurements, which can be carried into actual construction.