The Rocker from ISC is another useful device. Can be used as a backup device for rope access or as a rope grab or flip line grab. The rocker is very easy to adjust, it follows you up and down the rope. Just push the thumb swivel to lock it in position on the rope.
Here is ISC's Description-
The Rocker can be fitted to the rope at any point. It can be used hands-free when travelling up and down the rope. The Rocker has been designed for use without a Shock-absorber.
The Rocker can also be used as a Rope Adjuster on a Work Positioning Lanyard or Flip-line (in accordance with EN358).
The Rocker is a self-tailing device, but the Thumb-catch can be used to park the device on the rope, for Work Positioning or use as a Rope Access back-up device. The Rocker is fitted with non-aggressive 'rope friendly' cam faces.
The Rocker is suitable for 2 person load (maximum dynamic load rating 200kg)