Here is a sample of 6-pair "bird wire". Not shown is the steel support wire that was wrapped with the 6 pairs, and was no bigger diameter than one of the single insulated wires. Also shown is a 105A terminal (cover removed), which was held in place by a rear bolt/clamp to the support wire. This terminal allowed connection of a single-pair subscriber "drop" wire to one bird wire pair, as shown. The Bell System "BSP" Practice actually refers to bird wire as "Multiple Wire"