Monocular as in missing an I. Of the four I beams originally mounted on this dock, I imagine as spacers, though I'm not really confident, only this one remained. As with the two at the other end, the missing one on the right was torn out despite being anchored in a web of rebar. I don't even have a guess as to the purpose of the rollers on the dock's upper surface. The "No Trespassing" stencils were an attempt to keep visitors from climbing up onto the structure, and were not terribly successful. There were at least two kids up there during a part of our visit, who must have had a boost from parents. My recollection is that the powers that be were concerned about the dangers of falling off.