Precautions are in place to prevent anyone falling down the cellar opening, including the use of barriers, signs and a supervision of the delivery area. Access to the cellar is restricted during delivery operations. Skids (delivery rails for barrels to roll on) are maintained in good order. Gas cylinders are always connected to a reducing valve; never directly to beer containers. Cellar flaps at delivery openings must be able to be locked in the open, vertical position. Bottle crates and boxes are not stacked more than four cases high