A great way to prevent any of your gear getting stolen is the Sea to Summit Lockable Tie Down. Sea to Summit uses an innovative system that is the combination of stainless steel reinforced webbing with a super bomber lock to protect your "on top of car" gear.  After a long day paddling, surfing, biking or snowboarding, the first thing you want to do is eat.  So you pull into the restaurant and wait for that perfect space where you can keep an eye on your car, stressing a bit about someone yanking your most favorite play thing off your car.