9. Now this is important!! Don't tighten it with the socket wrench until you've snugged it with your hand. Let me explain. You plac the plug in the socket, attached the extension and with your fingers, gently place it into the hole and turn clockwise with your fingers. If it tries to cross thread, you'll notice it immediately. Remember, these plugs take several rotations to seat all the way down, so if it cross-threads, you'll know quickly. After it snugs, you can then tighten it with the socket wrench. The back of the Denso package shows that a non-tapered plug like the IK20 should be tightened 1/4 to 1/2 turn when you do the final tightening. This will properly seal the metal gasket. Do NOT overtighten the plug, as you may strip the threads.