Rotation stopper 

Clamp size	Code	Dim.	STEP
B	UBP-16
D	UDP-25

In some cases, the clamp tends to rotate around the bolt. This is typical, for example, for the clamps with self-adjusting balls in both jaws (-E).

To prevent rotation a rotation stopper plate can be used. Grooves to be made in the base platform where clamp is bolted to ensure that the plate sits firmly in the groove.