1975 Volkswagen Beetle Adjusting rocker arms.

If you mean valve lash, use a feeler gauge and 13mm wrench on the locknut and screwdriver on the adjusting screw. You want it so the gauge just slides between the tappet and the valve stem. Set intakes at .004 and exhaust at .006. Be patient and make sure it's still right after you tighten the locknut. Of course you have to make sure both valves are closed. and push in at the bottom of the rocker to take any slack out of the valve train.