How do I install roof rack cross rails on my 2005 Ford Freestar?

I just bought cross rails for my 2005 Ford Freestar but there is no groove in the factory installed rails that run from the front to the back. If you do not know the answer is there a website where I could find an answer?How do I install roof rack cross rails on my 2005 Ford Freestar?When new, the roof racks are installed at the dealer by the tech performing the PDI. There are end caps at the very rear of the rails. These caps are installed AFTER the new factory rails are installed, and slid into their appropriate areas on the roof. The rails themselves, have "knobs" on each end that tighten it down to their desired locations on the roof. The end caps simply clip into place when installed during the PDI procedure, so removing them shouldn't be very difficult. Hope this helps.