1. Marks or notches, usually located on the vibration damper , used to synchronize the ignition system so that the plugs will fire at the precise time.
2. One tooth on either the camshaft or crankshaft gear will be marked with an indentation or some other mark. Another mark will be found on the other gear between two of the teeth. The two gears must be meshed so that the marked tooth meshes with the marked spot on the other gear.