Simple steps for easy installation:<br>1. Simply place your spark plug into the gap tool.<br>2. Use your desired size feeler gauge for gap thickness.<br>3. Turn the knob with the feeler gauge in place till the side electrode compresses to the desired gap thickness.<br><br>NOTE: Some spark plugs electrode will spring back - This is normal for some spark plugs<br>If your gap target is 0.44mm we suggest to use 0.42mm this way when it spring back you will get it to 0.44mm.<BR>Please note that will vary on every spark plug brand, manufacturer, material of the spark plug.