The busiest men in sumo are the yobidashi (ring announcers).

Named after their most conspicuous duty, yobidashi do far more than just call rikishi up to fight.

In fact, pretty much every behind-the- scenes task in Japan's national sport is taken care of by sumo's unsung heroes.

Even the ring itself is built by yobidashi, in a physical and time-consuming process, over the course of several days in the run-up to each tournament.

In the stables, yobidashi run errands, record training bouts, assist the stablemaster, and perform a myriad of duties.

During tournaments, they ensure the smooth running of each day's schedule, often telling younger rikishi where they need to be and what they need to do.

The yobidashi set up the ring early in the morning and keep it in good condition throughout the day. They sweep and water the surface, make sure there is enough salt, power water and power paper, give wrestlers a towel before their bouts and carry advertising banners around the ring each day.

Their attire consists of a kimono and traditional workmen's clothing, often with sponsor's names on the back.

When calling out rikishi names yobidashi hold a plain white folding fan out in front of their face. That is done to prevent spittle falling on the sacred surface of the ring.

Most yobidashi begin their sumo life at age 15 and, like everyone else in the Japan Sumo Association, retire at 65. Promotion for yobidashi is based on seniority, which ensures a gradual move up the ranks over the course of a career.

The drumming that announces the start and end of each day's action is performed by yobidashi at the top of a tower located near the entrance to Ryogoku Kokugikan.