Single-adjustable shocks are pretty straightforward. By turning the knob, you either increase or decrease both rebound and compression damping. This is illustrated by this graph from Alston's shock dyno. As you can see, however, the rebound damping increases more than the compression damping-there's a usable range of adjustment, making a single-adjustable shock far superior to a nonadjustable one. It is limited, however, since both shock actions are adjusted together through 16 settings.