When it says "leather strip" that means the factory installed plastic trim. Remove the front and rear undertrim and leave the center one. You will remove (1) screw but when installing the bars you will use (2) in each. When it says "cotton backing" that means the peel off foam pads. After removing the factory plastic trim, cut off 11-3/4" from each end (30cm). You may have some difficulty with the screws, as the instructions say, we used a TEC screw to form threads, otherwise the factory screws may strip out. You can use a tap, match the threads which are fine. Before snapping on the ends, make sure you have the Left-RIght-Front-Back since if you make a mistake they are extremely difficult to remove (but removable using two flat screwdrivers carefully). Overall a nice looking and very sturdy set.