A man goes into a restaurant and the maitre'd stops him.

"Sorry sir, you need to wear a tie to enter".

So the man goes back to his car and looks around, but there's no necktie to be found. So he takes his jumper cables, wraps them around his neck, ties a nice knot, and lets the ends dangle about.

He goes back to the restaurant, where the waiter says, "Well, OK, you can come in......

....Just don't start anything."