Fuente: WIPO "rice" 21,253. Clark, R. O. Sept. 25. Man-hole and hand-hole doors for drains. - The cap F is confined within up-standing walls C and forms a tongue and groove joint at the sides with the pipe, trap, or the like. The joint is made tight with pipe-clay R. The cap may be kept in place by one of the following means : rods or wires passed through holes in the walls, as shown ; pivot pins on the cap and slots and bearings in the walls, or vice versÔ; cement above a layer of clay ; a loose cross-bar taking into crescent-shaped slots in the walls; a spring bar taking into holes sunk in the walls; or a pin hinge on one wall and a catch on the opposite one.