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Ignition points are adjusted to control the point-open gap. The point gap is typically around .018 to .020 inch. Adjusting the point gap also adjusts the dwell angle, which determines how long the points "dwell" in the closed position between spark-plug firings. This is determined in degrees of point dwell angle. When the points are closed between firings, the coil builds the current necessary to fire the spark plug. As the points open, the rotor crosses the terminal with the coil discharging the high-voltage spark to the spark-plug wire.