The timing gear is connected by chain, gears, or a belt to the crankshaft at one end and the camshaft on the other. It is marked with tiny increments all around its perimeter, which correspond to degrees of timing from the straight-up timing position of the camshaft and crankshaft. These marks assist the individual who is tuning up the engine to set the timing to the determined optimal timing degrees of the camshaft and engine designers.