braces are lashed the frame must be square by checking the
measurements of the diagonals.

If necessary, pickets for the foot and guy ropes are driven, the
former about 2 paces from the bank and 4 paces on each side of the
axis of the bridge; the latter about 20 paces from the bank and 10
paces on each side of the axis. The foot ropes, _CC_, Fig. 5, are
secured by timber hitches to the butts of the standards and the back
and fore guys, _DD_ and _EE_, to the tips the fore guys are passed
across to the opposite bank. The guys of the _narrow_ frame should be
_inside_ the guys and standards of the wide frame.

The frames are put into position one after the other, or
simultaneously if there are enough men. A man is told off to each foot
rope and one to each back guy to slack off as required, two turns
being taken with each of these ropes around their respective pickets.
The other men raise the frame and launch it forward, assisted by the
men at the fore guys, until the frame is balanced on the edge of the
bank. The frame is then tilted until the butts rest on the footing, by
slacking off the foot ropes and hauling on the fore guys, Fig. 5.
After the head of the frame has been hauled over beyond the
perpendicular, it is lowered nearly into its final position by
slacking off the back guys. When the two frames are in this position
opposite each other, the narrow frame is further lowered until its
standards rest upon the transom of the other. The wider (outer) frame
is then lowered until the two lock into each other, the standards of
each resting upon the transom of the other.

The center or fork transom, Figs. 3 and 4, is then passed from shore
and placed in the fork between the two frames. This forms the central
support to receive a floor system of two bays, built as already
described.

The estimated time for construction of such a bridge is about one hour
if the material is available and in position on both sides of the
stream. The construction of the roadway requires about twenty minutes;
forming footings in masonry about one hour.

=1114. Construction of double-lock bridge=, Fig. 6.--Suitable for
spans not exceeding 45 ft., and consisting of two inclined frames
which lock into a connecting horizontal frame of two or more distance
pieces, with cross transoms, dividing the gap to be bridged into three
equal bays of about 15 ft. The force required is two or three
noncommissioned officers and 25 to 50 men; the time for c