These men were cutting rebar. The man on the ground would place a chunk of railroad track on top of a large chunk of wood. Next he placed a long length of rebar on top the of the piece of railroad track. He then placed a shorter piece of rebar that he held onto over the spot he wanted to cut, and he placed a hook around the rebar that was on the right side of the track. Then the man with the sledge hammer came crashing down with his hammer and cut the rebar slicker than a whistle. This is how they were cutting all of the rebar for the construction of the new building that was going up nearby.