Some of the physical activities performed by Structure Maintainers - Group D and environmental conditions they experience are: working outdoors in all weather conditions, walking along subway tracks, stepping over rails (including live third rails), and climbing and walking on elevated structures and along trackwalks and catwalks in dimly lit areas; climbing and working on roofs, ladders, ramps and scaffolding; lifting and carrying heavy tools and equipment; bending and stooping in confined spaces; using hand tools and heavy-duty power tools; reading prints and drawings; distinguishing colored light signals; judging distances of lights in tunnels; and hearing warnings (bells, whistles and vocal) and responding to the sounds of oncoming trains. Responsibilities: Structure Maintainers - Group D, under general supervision, perform sheet metal work in subway, surface and elevated structures, including stations, enclosures and related buildings; install, maintain and repair roofs, skylights, ducts, leaders and gutters, drip pans, fireproof doors, stovepipes and receptacles; fabricate sheet metal, plastic and fiberglass parts and devices needed for such work; perform other structural work as necessary, including incidental painting; load, unload and drive trucks and vans; keep records; and perform related work.