It is generally desirable that the outer door of offices shall be fitted with a cylinder escutcheon lock. The most convenient lock for an office door is believed to be a cylinder latch with stop work similar to the vestibule latch, Fig. 385, as it is of great convenience in enabling the door to be made fast when leaving, without being obliged to stop and use a key. To prevent any instrument from being forced through the wooden stop of the door jamb to the beveled edge of the bolt, and thus forcing it back, the Yale protected strike (Fig. 390) has been introduced, which gives to the latch all the security of a dead bolt. This strike is applicable to all latch bolts, but must be made to order to correspond to the exact thickness of the door. The Russell 8c Erwin Manufacturing Co. make a special office door latch with a supplemental bolt which automatically locks the main latch when the door is closed, so that it cannot possibly be forced back. In important office buildings all of the office doors are master keyed.

Another arrangement for office doors which is preferred by some, consists in using a good three-tumbler lock and putting on a supplemental cylinder rim night latch, which may be changed or a new cylinder obtained with a change of tenant. The advantage of this lies in the fact that duplicate keys are often given out, some of which maybe lost or may not be returned when the office is vacated, and thus some unknown person may have access to the office. By changing the lock such possibility is avoided. If a single mortise cylinder latch is used, however, the same result may be obtained by purchasing a a new cylinder, as the cylinders of each manufacturer are interchangeable.

Fig. 390. - Yale Protected strike.