Audio Damage Dr. Device - Manual (Page 13)

With the LOCK setting, the nubbies are connected
together. Moving either nubby moves the other by the
same amount, and clicking either nubby also causes
the other nubby's Z-axis value to also change from
zero to one. A solid line appears between the nubbies
when the LOCK mode is engaged.
With the LINK setting, the nubbies are connected
together but the dark-colored nubby can be moved
independently of the light-colored nubby. Moving the
light nubby moves the dark one by the same amount,
but moving the dark nubby does not move the light
one. Clicking the dark nubby does not cause the light
nubby's Z-axis value to change. The LINK mode lets
you change the relative position of the nubbies
without disconnecting them. A dotted line appears
between the nubbies when the LINK mode is
engaged.