Two guards, A and B ([Fig. 208]), made as in [Fig. 216], protect the bolts and act as guides to keep them from swinging out of position; two springs C and D ([Fig. 208]), made of well-seasoned hickory and attached to the battens on the door by nails or screws, force the bolts down and up into the bolt-holes ([Fig. 208]). To release the bolts, the spring must be drawn back as shown by the dotted lines in [Fig. 208.] This may be done by means of a string or picture wire, which is fastened in the ends of the bolts and runs through a hole in the ends of the spring and is attached to the lever E ([Fig. 208]). When the end of this lever is pushed down into the position shown by the dotted line and arrow-point, it lifts up the Hall bolt at the bottom of the door and pulls down the Billy bolt overhead, thus unfastening the door.
[Fig. 208.] [Fig. 209.] [Fig. 210.] [Fig. 211.] [Fig. 212.] [Fig. 213.]
[Fig. 214.] [Fig. 215.] [Fig. 216.] [Fig. 217.]
Jack-knife latches suitable for Canada and America.
But, of course, if one is outside the door one cannot reach the lever E; so, to overcome this difficulty, a hole is bored through the central batten of the door and the latch-string is tied to the top end of the lever and the other end is run through the hole bored in the door ([Fig. 208]).
The end outside of the door is then tied to a nail; by pulling the nail you pull down the lever E, which undoes the bolts and opens the door.
When it is desired to leave the door locked, after it is closed, push the nail into the latch-string hole so that only the head will be visible from the outside. When the nail and string are arranged in this manner, a stranger will see no means of opening the door, and, as there are many nail-heads in all rough doors, the one to which the latch-string is attached will not attract the attention of any one who is unacquainted with the Deming twin bolt.
