A timing mark is an indicator used for setting the timing of the ignition system of an engine, typically found on the crankshaft pulley (as pictured) or the flywheel, being the largest radius rotating at crankshaft speed and therefore the place where marks at one degree intervals will be farthest apart. Modern engines usually use a crank sensor directly connected to the engine management system. The term can also be used to describe the timing patterns used in some barcodes, such as PostBar, Data Matrix, Aztec Code, etc.