13 Shirasu: This is very simplified today, but at the time when the Noh stage was in the open air, the space between the audience sheets and the stage was covered with gravel.
13白洲（しらす）　現在では簡略化されているが、能舞台が戸外にあった時代には客席と舞台との間に玉砂利を敷き詰めていた。