I use BareCraft roof racks (just like Thule and fit all Thule accessories but less cost) and use the blue foam kayak saddles. These are great because you can sand them to fit your boat exactly. I set the kayak on the foam and then use a strap with a ratchet to snug it down. Tie off the bow to each corner of the front and I'm set. For a little added protection I add two lines in the back, but usually I don't even need those. When tieing the bow and stern, don't pull too hard due to possible stresses caused when the car flexes.

As far as locking the boat goes, I have a cable I pass around the cockpit coaming and lock it to the roof rack. At least enough to keep the honest thieves at bay.

Hope this helps.

: would like to get info on mfg of roof racks for kayaks