I have two kayaks and I bought only one of these after Cambridge Kayaks advised that the second kayak could lie flat directly on the roof rack. However I ended up buying a second one anyway as it's much easier and more secure to strap the kayak to these J bars than direct to the roof rack. Once the J Bar is assembled, it just clamps to the roof rack in a minute or so. A quick release clamp would have been better but they're ok as they are and hold the kayak securely
