The Watts linkage can be either “axle mounted” or “chassis mounted”. This refers to the location of the Watts lever pivot axis.

Axle mounted Watts link pivot.

There are three chassis mounting points, one for the torque tube ball joint, one for each Watts link.

There are three axle mounting points, one for torque tube ball joint, and two for the Watts pivot, one of which is reference point to determine the pivot axis.

Chassis mounted Watts link pivot.

There are three chassis mounting points, one for the torque tube ball joint, and two for the Watts pivot, one of which is reference point to determine the pivot axis.

There are three axle mounting points, one for torque tube ball joint, one for each Watts link.