The Zigzag mechanical prusik for arborists combines all the individual pieces of gear being used in doubled rope climbing into a single mechanical prusik that operates just like climbing on a hitch and prusik in DdRT.
Friction is managed by running the climbing line through the linked "zig-zag" pattern of rings. The top ring is a lever; pushing down on this lever releases pressure in the rings, and the climber descends - just like using a prusik cord. Release the lever and the Zigzag jams, stopping descent. The climber has control over the rate of descent through varying the pressure on the Zigzag lever.
The attachment point for the climbing harness on the Zigzag is on a built-in swivel for twist-free ropes while you climb, which also helps make advancing the Zigzag smoother. The Zigzag has an eye for attaching the end of your climb line directly to the device in doubled rope climbing. Slack tending the Zigzag is made super-efficient with the built-in, sealed ball-bearing pulley.
The Zigzag accepts ropes from 11.5-13mm, so it works on your favorite 7/16" and 1/2" climb lines.