The Yakima HullHound is a set of 2 saddles and needs to be paired with HullyRollers or another set of HullHounds to carry one boat. No tools needed to attach to any crossbar out there, and comes with 1 strap and 1 tie-down.
The Yakima JayHook is a pair of J-style kayak carriers for holding a kayak on its side on your vehicle's roof rack. The JayHook is designed to carry all types of kayaks, from whitewater to recreational to touring, including tandems.