 During construction, they served as the rails that supported and guided the trolleys on which the glaziers sat as they installed the roofing.Once completed, the channels acted both as the joists that supported the roof sections, and as guttering—a patented design now widely known as a "Paxton gutter".These gutters conducted the rainwater to the ends of each furrow, where they emptied into the larger main gutters, which were set at right angles to the smaller gutters, along the top of the main horizontal roof bearers.