7. The erector of claim 6 wherein the extremities of the yoke arms each have a tip, the tips being in abutting contact, the extremities being in mutual contact along a portion of their length, and upon rotation of the yoke arms relatively further apart, the extremities rotate correspondingly relatively further apart, the tips remaining in abutting contact as the extremities rotate.
7. The erector of claim 6 wherein the extremities of the yoke arms each have a tip, the tips being in abutting contact, the extremities being in mutual contact along a portion of their length, and upon rotation of the yoke arms relatively further apart, the extremities rotate correspondingly relatively further apart, the tips remaining in abutting contact as the extremities rotate. 8. The erector of claim 7 wherein the extremities rotate about a pivotal axis, the pivotal axis located essentially at the point of contact between the tips, the tips rolling one upon the other in correspondence to the rotation of the extremities.