The Japanese name for the starting lines on a professional sumo ring is shikiri-sen.
The shikiri-sen are the two white lines painted near the center of the dohyo. Wrestlers crouch behind these lines before the tachiai, the explosive initial charge that begins a bout. They must not touch the area beyond the lines before the start.
The pre-bout preparation period is called shikiri. During it, wrestlers face each other, perform ritual movements, and repeatedly return to their corners before finally committing to the charge. The lines provide a clear visual boundary for that final positioning.
The shikiri-sen are sometimes confused with the tawara, the rice-straw bales forming the outer boundary of the dohyo. The lines are painted markings; the tawara are physical objects that define the edge of the ring.