The fundoshi is used not only in a case of misogi or suigyo, a purification ceremony particularly in cold water, but also in some of hadaka matsuri (literally, naked festival in which men are naked except for fundoshi loincloths).
禊（水行）の時に使われる場合が多い他、一部の裸祭りでは六尺褌に代って、こちらが使われる場合がある。