Locks on both sides of the adapter release the M42 mount for full 360 degree rotation.
The locks engage a gear like ring on the mount and lock in small steps.

This of course allows swings and tilts and rise and fall in any position. In addition, this arrangement allows making up variations of thread positions in M42 adapters so the lens can be correctly centered regardless of adapter used.

The very clever shift adjustment is released by pushing down on the index tab on the "top".
The lock engages a fine rack that has 1mm detents.

Once pressed down, you simply slide the lens into the desired position and release,
locking in that position.
This quickly becomes intuitive and quick and is much better than a fiddly screw lead adjustment used in many T/S lenses.
There is a mm scale across the "top" of the dovetail, 15mm to each side.