Since many years ago www.4x4proyect.com import the famous Soft tops from Bestop Manufacturing, the part number, BST75146-15Side Bars fit on GMC Silverado/Sierra Crew Cab 1500, 2500, 3500 Crew Cab for years 2011 at 2018
It's the board that moves. Automatically extends down when you open the door, then retracts smoothly andt tucks up underneath the body. You get OEM look, function, and reliability for less than factory boards.