Here are a couple of car keys from two different brands:
On the left, you have the lock button up the unlock button down.
On the right you have the unlock button up, and the unlock down.
The first has two raised bumps on the lock button and no bumps on the unlock.
The second has one bump on the unlock and no bumps on the lock button.
It's simply impossible to lock and unlock the car without getting the keys out of the pocket and looking at them.