Jumars offer similar functionality as prusik knots but are stronger, faster, safer and easier to use. A jumar employs a cam which allows the device to slide freely in one direction (usually the intended direction of movement), and provide a firm grip on the rope when pulled on in the opposite directionoun To prevent a Jumar from accidentally coming off the rope, a locking mechanism or trigger is deployed. The Jumar is first attached to the climber's harness by a piece of webbing or sling, and then the Jumar is clipped onto the rope and locked. For climbing on a fixed rope attached, for example, to snow anchors on a steep slope, only one Jumar is used as the other hand is free for holding an ice axe.