598

ON LOCKS ANI) KEYS.

internal parts have been brought back into then-original position. This object is effected by thebarrel and curtain combined , as when the key orother instrument is introduced and turned roundin the keyhole, the curtain or shield b (fig. 256)is carried round inside the lock, and covering upthe hole, thereby prevents the introduction of a

Fig. 356.—Restell’s Lock.

second instrument. So far there is nothing new inthe invention. In order to prevent the key frombeing turned in the wrong direction, a projectingstud or tooth, /, (fig. 257), is formed on or attachedto the periphery of the curtain; and when thebarrel and curtain is turned round either way, thistooth or stud will be brought against one side orthe other of the bit or stud on the bolt, and the keywill be thereby prevented from going round anyfarther. The tooth also serves to hold the barreland curtain in the proper position to receive thekey, as unless some precaution of this kind were