The lugs are a one-way design. They provide a 90° surface for the ears on the crank to push against when turning the engine and a tapered incline which forces the crank out of the lugs when turned the other way or when the engine starts.

Save a life, adopt a senior shelter pet.
The three main causes of blindness: Cataracts, Politics, Religion.
Name your dog Naked so you can walk Naked in the park.