A clamp apparatus (20) for selectively occluding a tube comprises a base member (22) to which the tube is attached or through which it passes, and a slide clamp (24) that slides relative to the base member and relative to the tube. The aperture (38) in the slide clamp has a relatively open hole, through which the tube passes when the clamp is an open position, and a relatively constricted slot preventing fluid flow through the tube. A deflectable cantilevered locking arm (60) on the base interlocks with a detent (48) on the slide clamp to lock the slide clamp at the occluding position. A release tab (64) to release the locking arm from the slide clamp is located off center to avoid inadvertent activation. The deflectable arm is unstressed when the slide clamp is in either the occluding or the open positions.
