Strap canoes to the crossbars using 1″ nylon straps with padded stainless steel cam buckles. Pass the strap under the far side of the bar, doubling it over the hull. Double loop the free end around the near side before tensioning it through the cam lock buckle.
Excess strap webbing must be trimmed so as to not reach tires; melting the new end. Loose ends can be tied off or looped under the strap.
Bow lines limit sideways bow movement in the windstorm created as a vehicle runs down the road. Loop two individual ropes or straps around the front grab bar and attach to the vehicle to limit side to side bow movement and backwards hull slippage. Web loops tied to the frame just under the hood are more secure and wider attachment points than hooks under the bumper and prevent ropes from rubbing paint.
Double cut foam blocks suffice to carry a single hull on a vehicle with factory roof racks. The blocks are positioned on the cross bars, and the rails slipped down into cross cuts. Strap the hull down as above, using double bow lines.
A canoe may be strapped to vehicles without roof racks using the same foam blocks. Two straps run through the car doors or rear windows (open the doors before running straps through). Position the blocks directly under the straps and use double bow and double stern.