Sometimes when the bow-string has been hitched by hand over the catch
of the lock preparatory to bending the bow with the lever (fig. 116, p.
180), the intention of doing so is changed. As the trigger in the stock
can only be worked when the bow is fully bent, this knob is often useful
in such a case for instantly loosing the string from the catch of the lock.
The trouble of lifting it off the catch is thus avoided.
In many of the older bullet crossbows the trigger in the stock was absent,
this small knob taking its place as the only means of setting free the
bow-string when the bow was fully bent.
Fig. 140. - The Frame of the Fore-Sight, with Its
Small Skein of Thread Stretched Between Two Metal Rings. Half full size.
The frame that holds the bead which acts as a fore-sight is the notched
steel fork attached to the fore-end of the stock, F, fig. 115, p. 178.
This fork hinges down when not required.
To arrange the fore-sight:
(1) Obtain a couple of metal rings 1/4 in. in diameter, such, for instance,
as are used for the top joint of a salmon rod.
(2) Place one ring on one arm of the notched fork and the other ring
opposite to it on the other arm of the fork.
(3) With a needle and a couple of feet of black sewing cotton, connect
the two rings together, so as to form a tight little skein (of about a
dozen strands) between the upright arms of the fork, fig. 140.
(4) Take another length of black cotton and wrap it closely over this
little skein and to within 1/4 in. of each ring.