{HEAD ~ A stair cleaning device} intended for cleaning the steps and risers of stairs and other confined areas comprises {TAIL ~ three heads} driven by a motor and a belt and pulley system 
comprises
{ HEAD ~ A stair cleaning device } intended for cleaning the steps and risers of stairs and other confined areas comprises { TAIL ~ three heads } driven by a motor and a belt and pulley system
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH