Abstract: A locking device for a circumferentially grooved reciprocating member is disclosed. In one embodiment the locking device includes a housing, through which the reciprocating member passes, having a pair of spring biased locking elements and a release element disposed therein. Locking is achieved by insertion of the locking elements into the reciprocating member circumferential groove. Unlocking is effected by displacement of the release element towards the locking elements along a line perpendicular to the reciprocating member to withdraw the locking elements. In an alternative embodiment a spring biased retention pin is provided to selectively engage and retain the release element in proximity to the locking elements. An annular ring may be disposed about the reciprocating member adjacent the circumferential groove to displace and disengage the retention pin from the release element.