The vendors loaded a small boiler to clean pipes with its steam and put the rau on top of the steam exhaust vent of the boiler to make a sound like the steam locomotive whistles to signal their presence.
小型のボイラーを積みその蒸気で掃除をし、また蒸気の出口に羅宇を被せ蒸気機関車の警笛の様に「ぴー」という音を出して知らせた。