Arca Style Parallel Dual Clamp (F9130)
Small screws at the edge allow a plate or rail to be fixed to the Dual Clamp, independent of the main locking knob of the clamp. This allows lens rings to be mounted one by one safely and allow the Dual Clamp be fixed to one rail while moving or adjusting the second rail. This feature is ideal when mounting a lens ring or telephoto lens plate atop of another rail.
Because both clamping jaws are simultaneously closed by the main locking knob, all plates or rails used with the Dual Clamp need to have exactly the same dovetail.