Locked keys inside car

You slip it in between the weather stripping and the window, with the angle of the Jim oriented toward the door lock. There are a series of rods that connect the inner and outer handles with the door lock, so you just have to push down, or maybe lift up and move it around until you find a rod. It will help you greatly if you can find online a picture of what the exploded view of your lock assembly looks like. Once you hook a rod or press on one, you'll just have to experiment until you pop it. Beware: Some newer cars have plates welded inside to prevent slim jims from working.