A B frame was now hauled out to one of the towers and lifted by its narrower end, with fall and tackle, until its lower tie piece rested on the projecting ends of the center crosspieces of the tower. The upper end of the frame was held against the top of the tower, while a C frame was hooked over the upper ends of the tower legs; then frame B was allowed to swing outward until its smaller end locked with the outer end of frame C. It will be observed in Fig. 306 that the upper crosspiece or tie piece of frame B was fastened to one side of the vertical sticks and the lower tie piece to the other side. This was done purposely, so that when the frame was set in position the bottom tie piece would be on the lower side of the frame and the top piece would lie on the upper side, as shown in Fig 318, or, better still, in Fig. 319.

Fig. 318. View of Part of the Bridge, with Letters Indicating the Various Frames.

The rest of the frames were all arranged to be set in place with their tie pieces on the lower side, or facing the towers, as will be clearly understood by examining the illustrations. As soon as the B and C frames were set up on one side of the tower, another pair of B and C frames was set up on the other side of the same tower. A cantilever bridge must always be built out on both sides of the tower at the same time, otherwise it will be overbalanced on one side and topple over. After the B and C frames were in place we took two D frames, with oppositely cut ends, and rested their tie sticks on the top of the tower, just under the ends of the C frames. The ends of the two D frames overlapped at the center of the tower, and, as one was cut away at the outer side and the other at the inner side, they fitted neatly together and were fastened with bolts. The D frames were supported near their outer ends with E frames, which rested on the B and C frames. Fig. 319 shows an E frame set in position on the landward side of the tower, while two of the boys are climbing out on the opposite B and C frames preparatory to setting up the other E frame. A cross stick was now bolted to each D frame, just beyond the upper ends of the E sticks. This done, the frame F was hooked in between the ends of B and C, at the shoreward side of the tower, and its outer ends were supported by frame G, which was hooked over frame D and the upper ends of frame E. The frame L was then rested on the ends of frame F and G, and supported the shore end of frame D. A stick nailed across frame D on each side of the upper ends of frame L served to hold the latter in place.