The door shows the two strings _H_ and _K_ coming through gimlet holes
near the top. Fig. 218 represents the outside of the door. The strings may
be concealed by covering their ends with a board as shown in this diagram,
but even if they are not concealed, one unacquainted with the lock will
not know how to work them in order to open the door.
_A_ in Figs. 219, 220, and 221 is the latch which is made of a piece of
wood about eight or nine inches long by about one and one half inches wide
by an inch or three quarters of an inch thick. A hole is drilled near the
centre of the latch and a screw placed through which is screwed into the
door so that the latch will extend about two or three inches beyond the
end of the door.
_D_ (Figs. 219, 220, and 221) is a catch or stop which is fastened to the
door-jamb and keeps the end of the latch from flying too far up to lock
the door.
_B_ (Fig. 219) is the key which is made of the same sort of wood as the
latch; a hole is drilled in this also but it is here placed about one inch
from the top. A screw is run through this, as in the hole in the latch,
and screwed into the door (Fig. 219).
Fig. _C_, 219 is a small block of wood on which a steel-band spring has
been screwed to keep the key in its proper place. The block is screwed to
the door a short distance above the top of the key.
Fig. _J_, 219 is a nail or peg placed in the door close beside the key
when the key is vertical; this is intended to prevent the key from being
shoved over too far by the force of the band spring _F_.
Fig. 219 _L_ is a steel wire spring (a window-shade spring will answer the
purpose), fastened to the door at one end and to the latch at the other
end, and serves to keep the latch down and in place when locked.
Fig. 219 _K_ is the latch-string, one end of which is fastened to one end
of the latch and the other end run through a hole near the top of the door
and extending outside the same as the latch-string (Fig. 218).
Fig. 219 shows the positions of the latch and key when the latch is
locked; to open the lock from the outside it is necessary to pull the key
string first (_H_, Fig. 220), which releases the key; then pull the
latch-string, thus lifting the latch while still holding the key string.
The key string is now let go; the spring forcing the key into the position
shown in Fig. 221 will keep the door unlocked.
When leaving the room, all that is necessary is to pull the key string
which lifts the key, then let go the latch-string, and the latch will
spring back to its locked position and the key will also fly back into its
position as in Fig. 219. Any one not knowing the combination will be
unable to open the door.
Fig. 218. Fig. 219. Fig. 220. Fig. 221. Fig. 222. Fig. 223.
Fig. 224. Fig. 225. Fig. 226. Fig. 227. Fig. 228.
[Illustration: Home-made cabin door-locks.]