The locking mechanisms on different types of cars vary pretty widely. All newer models have power locks with remote controls to open them, but older cars open only manually. Also, some vehicles have the locking knob on the inside top of the door by the window, and others have it by the handle, which can change which way you go about it.
unlocking the car when you've left the car keys inside - don't forget the tennis ball!-If you're gonna keep a ball in your purse why not just keep spare keys in your purse. I guess trying to use a tennis ball would be more exciting.