A Z-Drag is an arrangement of lines and pulleys commonly used in rescue situations. The arrangement provides a mechanical advantage of three. The name comes from the fact that the arrangement of lines is roughly Z shaped.
The typical configuration (shown below) uses two
pulleys and two Prusik knotloops (sliding/gripping knots). The first Prusik knot provides the mechanical advantage. The second Prusik knot can be used to hold the position of the rope and is sometimes referred to as a 'progress capture device.' At least two people are usually needed to operate a Z-Drag since the Prusik knots require periodic adjustment. It is also advisable to attach a towel or soft object (such as a life vest) to the end of the line near the connection to the object being pulled since the line is under high tension and could break free and present a dangerous flying hazard.
The Z-Drag is considered an important tool in
whitewaterrescue and is used primarily for the recovery of pinned boats.
* Swiftwater Rescue: A Manual for the Rescue Professional ISBN 978-0964958500
* Whitewater Rescue Manual: New Techniques for Canoeists, Kayakers, and Rafters ISBN 978-0070677906
* River Rescue: A Manual for Whitewater Safety ISBN 978-1878239556
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