How do you tighten the shocks on a mountain bike?

they act as shock dampers. if you ride an unsuspended bike over rough terrain or even small bumps or rocks or any uneven surface, you will notice that the whole bike bounces a bit because the rock or whatever pushes the bike up. When you hit the same bumps or objects with a suspended bike the front fork gets shorter by sliding up therefore avoiding much bouncing by the rest of the bike, and the back wheel moves up too, but the positioning of rear suspension varies greatly by brand and bike. it is very simple really just look at your suspension as you ride over bumps.