steel of man

I wait to cross 58th Street, where they have been working and temporary plates of steel have been placed to cover the trenches.  Cars pass over the steel, an inch thick.  It gives an inch or so, but holds.  A dump truck filled to the brim with sand goes over.  The steel plate holds - an inch-thick plate of steel spanning a five-foot trench, holding up that passing weight.  A simple thing, but it awes me to think of what that material is doing, particularly on the stretching underside of the plate, the material holding itself together, no different than a cable stretched between two poles.  The passing truck, in every sense, depending from above.