You’ve purchased an accessories for your roof rack that fits in to the track on the top of the roof bar. This track is currently covered by a rubber insert strip to stop the roof bars whistling while your are driving.
To fit the accessories you need to remove the rubber strip and then slide your accessories on to the track and clamp them down. Some of the track will be exposed and therefore you need to cut the rubber strip in to smaller pieces. This will fill in the gaps so that the wind doesn’t whistle over the roof bars when you are driving.
Don’t want to cut the original piece of rubber up then buy a replacement piece from us.