This style of boat, both large and small, was once a common cargo-carrying craft used in the myriad canals of Tokyo. Tenmasen is a catch-all phrase for small Japanese workboats, encompassing ships boats, tenders, lighters, net-handling, and canal boats.

Canal boats such as these feature relatively heavy construction with thick planking, massive bow construction, and heavy beams. In the Tokyo region they also have extensive copper plating protecting the bow as well as covering vulnerable plank seams. The rails are wide and flat so the operators can safely walk along them, skirting cargo piled high in the middle of the hull. They were generally propelled by bamboo poles.