The rocker arm shafts have a notch in them that the bolt is supposed to butt up against, locking the rocker arm shafts in place. However, the bolt hole is too large, leaving a gap. This gap allows the shaft to rotate and hit the bolt, causing a tick.~See the picture where the bolts have witness marks from the rocker shaft rotating and tapping the bolts. This is what makes the annoying ticking/tapping noise.~The Rocker Lockers eliminate the gap, locking the shaft from turning and striking the bolt, eliminating that annoying tick. ~The Rocker Lockers also center the inner rocker cover so that it is always located in the same position eliminating different wear patterns on the rocker arm/valve and a better alignment of the pushrod in the holes. ~The Rocker Lockers are tapered so that they lock themselves in and wedge the bolt/shaft in place. ~It is recommended to replace the rocker base gaskets. This is the gasket that goes between the Rocker Cover Inner & the head on each cylinder. You can get these at your HD Dealership, or use the Cometic Gaskets we offer (sku: DK-RBG-COM) They are sold in a set of two, one for each cylinder.~The Drawing shows how the Teflon Centering Tool Makes installation Easy! ~Have you tried changing cams, replacing lifters, adjusting pushrods, different oils and still have that annoying ticking? Try the Rocker Lockers, they will eliminate the ticking from the rocker arm shafts. ~Please note~Rocker Lockers will not quiet noisy lifters, noisy chains, gears, tensioners or bearings. Rocker lockers keep the shaft from rotating and hitting the inner rocker bolts. ~If you ever need to remove the lockers, just use a punch and tap them out, they are usually reusable.~Patent Pending~ Fitment:Fits 2007 & up Sportsters - If you have a 1986-2006 Sportster or Twin Cams & Big Twin Evo's check out our other Rocker Lockers.~* While Step-by-Step instructions are included, it is recommended to also supplement them with the Service Manual.