=48. Asylum and Prison Locks.=—For the doors of cells in insane asylums, hospitals, and prisons, locks of special construction are required. For this reason, a distinct class of hardware is manufactured to meet the peculiar conditions that prevail. These locks, which are designed primarily to prevent escape from the rooms, or cells, are exceptionally exposed to attempts at tampering, and are especially constructed to meet these conditions. There is an extensive line of locks for these uses on the market. This line includes both the Yale type and the lever-tumbler type of lock, and these locks are constructed with both solid and barrel keys, thus affording a wide range of selection. All such locks must be made so as to be controlled by master keys. In Fig. 52 are illustrated types of prison or asylum locks. The lock shown at (_a_) is embedded, or built, in the jamb, while that at (_b_) is secured to the door and the keeper is fastened in the jamb. [Illustration: FIG. 53] There are numerous other patterns of asylum and prison locks, such as those illustrated in Fig. 53. The lock shown at (_a_) is arranged to operate with a double-bitted key, while the one at (_b_) is operated by means of a Yale key. Nearly all modern locks for this purpose are operated with either double-bitted or Yale keys, and those in common use are cylinder locks. Information regarding these types of locks should be obtained in advance, so that in preparing the plans and specifications, the type selected may be clearly indicated and the arrangements made for any special construction necessary to receive them. As the approved forms of asylum or prison locks are built in the masonry during construction, they must be delivered during the early stages of the erection of the building. =49. Bank and Safe Locks.=—Locks for the doors of burglar-proof and fireproof safes and vaults constitute a group distinct from all others. These locks embody the most complicated mechanism, and represent the highest art of modern lock making. The architect in preparing plans of buildings for banks and trust companies is frequently called on to approve or to specify the fastenings for vault and safe doors. While the owners of such buildings will probably predetermine the kind of lock to be employed, nevertheless they will be guided by the advice of the architect in the selection of some particular make. The locks used on such vaults and safes comprise _time_, or _chronometer, locks_; _dial_, or _combination, locks_; and _safe-deposit_ and _subtreasury locks_. There is also a device known as a _bolt-motor_, or _automatic lock_, which is an allied product. In the manufacture of these special locks, the skill of numerous experts and specialists is required, and as their knowledge is at the disposal of the architect or the engineer, they should be consulted in the selection of such important pieces of mechanism. [Illustration: FIG. 54]