A clamp apparatus for selectively preventing fluid flow through a resilient tube, comprising: a base having a tube aperture at which the resilient tube may be located, the base having a longitudinal center line; a slide clamp slidably mountable on the base for movement between an occluding position and an open position, the slide clamp having a longitudinal center line; a clamp aperture formed in the slide clamp for receiving the tube therethrough; a constricted region formed in the clamp aperture, the constricted region occluding the tube to prevent fluid flow through the tube when the slide clamp is in the occluding position; an open region formed in the clamp aperture, the open region allowing fluid flow through the tube when the slide clamp is in the open position; a flexible cantilevered locking arm mounted on the base, the locking arm being biased toward a locking position to prevent movement of the slide clamp from the occluding position to the open position, the locking arm being deflectable to allow subsequent movement of the slide clamp from the occluding position to the open position; and a detent in the slide clamp into which the locking arm is biased to the locking position and into which the locking arm is located when the slide clamp is in the occluding position to prevent the slide clamp from moving from the occluding position; the apparatus being characterized in that: the detent is large enough to receive the locking arm such that the locking arm is unstressed while in the detent; and the slide clamp further comprises a ramp to receive the locking arm when the slide clamp is in the open position, the ramp formed to be deeper than the arm whereby the arm is unstressed when the slide clamp is in the flow position. a base having a tube aperture at which the resilient tube may be located, the base having a longitudinal center line; a slide clamp slidably mountable on the base for movement between an occluding position and an open position, the slide clamp having a longitudinal center line; a clamp aperture formed in the slide clamp for receiving the tube therethrough; a constricted region formed in the clamp aperture, the constricted region occluding the tube to prevent fluid flow through the tube when the slide clamp is in the occluding position; an open region formed in the clamp aperture, the open region allowing fluid flow through the tube when the slide clamp is in the open position; a flexible cantilevered locking arm mounted on the base, the locking arm being biased toward a locking position to prevent movement of the slide clamp from the occluding position to the open position, the locking arm being deflectable to allow subsequent movement of the slide clamp from the occluding position to the open position; and a detent in the slide clamp into which the locking arm is biased to the locking position and into which the locking arm is located when the slide clamp is in the occluding position to prevent the slide clamp from moving from the occluding position; the apparatus being characterized in that: the detent is large enough to receive the locking arm such that the locking arm is unstressed while in the detent; and the slide clamp further comprises a ramp to receive the locking arm when the slide clamp is in the open position, the ramp formed to be deeper than the arm whereby the arm is unstressed when the slide clamp is in the flow position. the detent is large enough to receive the locking arm such that the locking arm is unstressed while in the detent; and the slide clamp further comprises a ramp to receive the locking arm when the slide clamp is in the open position, the ramp formed to be deeper than the arm whereby the arm is unstressed when the slide clamp is in the flow position.