I-stopcock yezindlela ezintathu isetshenziselwa ukuxhuma nemishini yokufaka ukuze kuxhunywe futhi kulawulwe ukujova ngomthambo, ukulinganisa ingcindezi nokunye.I-stopcock inezikhala ezintathu (izimbobo) ezingaxhunywa kumashubhu, amasirinji, noma ezinye izinto zokwelapha. Isibambo esimaphakathi noma i-lever ivumela abahlinzeki bezempilo ukuthi balawule indlela yokuhamba ngokuyizungezisa ukuze iqondaniswe nezimbobo ezithile.