A word of advice from someone who's tried -- you really can't get the keys apart.

A few months ago, I rented a car from Hertz. A parking attendant locked both keys in the car. I called Hertz, they sent triple-A, I’m charged $130. I said to the Triple-A guy, "If these keys weren’t attached I wouldn’t have had this problem."

He offers to cut them apart, and his bolt cutter couldn't even do it—that wire is like titanium or something.