_The Central Lock._—There is a grade of guns made with locks enclosed in the breech, or a continuation of the breech, in the same manner as common revolvers and other pistol locks are made. A view of this lock is given in Fig. 47. The principle is much the same as the back action lock when the hammer is placed on one side as in the back action lock. One side of the frame has the same office as the lock plate, and the other side supports the tumbler and other parts the same as the bridle. The formation of the tumbler is such that no sear is necessary, the trigger bearing directly against it; the point of the trigger having the same office as the nose of the tumbler, a small spring keeping it to place to catch in the tumbler notches. Generally this form of lock has the hammer placed directly in the central line of the bore of the barrel, and when so placed the lower end of the hammer has the same office as the tumbler and is shaped and has notches cut as in a side lock tumbler. As this form of lock has few parts, and has a long feather-like mainspring, it is easy and pleasant to operate. [Illustration: FIGURE 46.] _Cleaning Locks, etc._—While the gunsmith will be called upon to clean and repair various parts of fire-arms, the lock is the part with which he will have considerable to do. And, in most kind of guns, it is the most complicated part, and, consequently, the most difficult part to manage. Not a few gun-owners look upon it as a kind of mystery without the range of ordinary comprehension, hence they carry it to the shop, not only at the slightest indication of “something wrong,” but so often as it would seem to need thorough cleaning and oiling. This is all well enough, for the gun as much as anything comes clearly within the application of the rule which admonishes that “a stitch in time saves nine.” All of which being the case, one of the earliest things that the gunsmith will be called upon to study will be [Illustration: FIGURE 47.] _How to Take Down a Lock._—Having removed the lock from the gun, set the hammer at full-cock. Apply the hand-vise, or mainspring clamp, if he has one, to the mainspring, having first placed a bit of chamois skin or felt between the jaws of the vise and the spring to prevent bruising or scratching the polished surface of the latter. Turn up the vise gently until the hammer feels loose. Now press upon the sear-spring and let down the hammer. The mainspring is now entirely loose, and may be lifted out with the vise. This ends the complication of the lock; it is now only a plain machine, with parts held into position by screws, which may be removed one at a time until every piece has been taken from the plate.