Abstract: A safety device comprising a runner which can be threaded onto a suspended safety line and houses a linegripping member movable between an unlocked condition and a locked condition and an operating member which provides externally of the runner an attachment point for a personal safety belt and is operatively associated with the line-gripping member to cause movement thereof towards locked condition responsive to sudden downward acceleration of the attachment point; with the improvement that the operating member comprises first and second link members pivotally attached to the runner, and a bar member pivotally connected to the link members to form a parallel linkage, and that the attachment point is disposed at least as high as the level of the top of the runner housing when the runner is oriented for use on a vertical line with the operating mechanism in its runner-free position.