Your gonna love this. Bought my 06 DC back in August and had the chrome rails installed there at the dealership during the selling process. For some reason during the last 5 or so months, the rails kept getting loose and vibrated while you were driving and there was a lot of "play" if you were to grab the rail from the back at the end of the rail and lift, I mean...."allot" of play. Took it back to dealership 3 times for "re-adjustments" till finally I got fed up yesterday and looked under the truck to see how they were mounted (which I should have done anyway) and noticed the back bracket was mounted on the frame as it should but.........over some type of round rivet on the frame. The installer had used metal washers to compensate for the gap between the bracket and the protruding rivit on the frame to try and get a tight fit which did not work obviously. Then I noticed he had "drilled" into my frame on both sides having the same problem and used the same method both times. Then I discovered and had it confirmed that the rails installed on my truck were the wrong "size"...or length front to back. They were 6 inches too short and belonged on an Access Cab........"not" my DC!!! Why I did not notice the size difference till now I do not know. The installer drilled into my frame I guess thinking he could make it work and it didn't and no one was the wiser for it. My question is this: If factory rails are installed, are not the holes on the frame "pre-drilled" for such installation? Also, could any damage have been caused by the installer to my frame by "drilling those 4 extra holes? I mean, as far as the integrity of the frame is concerned?