Can't install threshold moulding

The old threshold molding on an exterior door wore out so I bought a new one. I got the aluminum plate fitted and installed, but I can't figure out how to put in the rubber seal. Here's a pic of the destructions, including an image of what the profile of the rubber molding looks like: Image: http://s1.bild.me/bilder/260513/9992956door_seal.jpg (http://www.bild.me) It goes on real easy, provided it isn't already screwed to the floor. But if the molding is installed, you can't put in the screws. I tried warming it in hot water to make it more pliable, but still couldn't get it to start. I thought about using aerosol hair spray as a lube, but don't have any on hand.