expression, godan verb (-su)
wear a sword; carry a sword at one's side
Refers to the traditional practice of wearing a katana or other sword thrust through the sash, typically at the left hip.
侍は腰に刀を差していた。
The samurai wore a sword at his hip.
Compound of 刀 (katana, 'sword') + を (object marker) + 差す (sasu, 'to insert, thrust'). The verb 差す here means to insert the scabbard through the sash.