Wrap a 3-shaku cloth as a makeshift belt.
The sumo wrestler ties his waistband and enters the ring.
帯 is the general word for a sash or belt, while 三尺 specifically refers to a 3-shaku length cloth used as a waistband, often in traditional or sumo contexts.
cloth waistband; traditional belt; obi
avid desire; drooling over; watering at the mouth
sharpened sword
mere child; small child
From 三 (three) + 尺 (shaku, a traditional Japanese unit of length). The waistband sense comes from the typical length of cloth used.