CIAssITICATION OF LOCKS. Locks in a general way may be classified according to the use for which they are intended, as follows: (1) Front door locks and vestibule latches• for entrances; (2) sliding-door locks: (3) night-latches: (4) store-door locks; (.5) deadlock,. in which no knob is used. the key action alone being required; (6) hotel locks, which are so arranged that when locked from the inside they cannot be unlocked from the outside of the door. :Mo•tise locks are mortised into the frame of the door. while rim locks are secured to its face. Master-keyed locks are so constructed that a single master-key can unlock a whole group or series. but there is also an individual key for each lock, which will operate no other lock in the series.
1.)tat. LOCKS. An important class of locks are what are called permutation and dial lock-, use•1 upon safes. (me of the principal deg ice, in then' is the employment of a number of wheel-, placed near together, on an axis on which they move independently. These wheel, do not inter fere with the mction of ea( h other, except wl en certain pins are brougl t in contact, the pins being movable at the will of the per-on adju-ting the lock. In this way one having knowled;.,I of the con bination may arrange the wile( Is so that certain slots in their peripheries w ill not coin cide• and cannot he male to coincide. by any one net in possession t f the arrangement. The per son having such knowledge may. however. readily place the slot: into line so that a lay may be passed through them, or a h •ndle operating the bolt ineel anism rth-a-ed and the latter nn vtd. Au ingeniouly arranged dial is place I on tl.e outside of the safe door. which a bolt
passes attached in the lock to a wheel. This fixed wheel can be turned tne way or another. and. being provided with a pin. the first of the movable wheel: may be turned so that it, -lot will cot-re-pond to any number on the dial. The firo movable wheel, being also provided with a pin upon its disk. is made to turn the --econd wheel to a certain position, and so on to the last wheel. when. the slots being all brought into line, the handle operating the bolt: is free to turn. There are a great many vanities of these locks. each possessing varicns advantage-. As burglars often compel the person having the knowledge of the combination of a lock to reveal the secret, it is often the practice to provide bank-vault lock- with a clockwork attachment by means cf which the bolt is liberated at t certain hour. until which time nobody• wit even the person possessing a knowledge of the com bination, can open the lock. A- powerful ex plosives • have been inserted through the key holes of locks. a time lock has been de vised for greater security. A ease eontaining two very powerful springs is placed on the inside of the door and operated by a key on the out side. One of these springs is released as the door is shut and throws the bolts into a locked position. The second spring is acted on by a clock movement, and at whatever hour the (.1. ek is set the spring is released and throws the 1), Its into their unlocked position. The owner. when closing his safe at night. set: the clock to rim fr guard at whatever hour he wishes, say nine o'clock the following morning. They may he -et to run seventy-two hours.