You will usually need two straps one for each crossbar.
How to tie a kayak down on a roof rack.
Run the bare end from the strap from the cam buckle.
Once the kayak is in position on the roof rack and the straps are laying over the kayak it is time to strap it down.
Run 2 boat straps over the top of the kayak and them under the roof rack bars then bring the straps to the other side of the kayak and loop them under the roof rack bars on that side.
Insert the bare end in the strap throughout the slot within the cam buckle and move it through together with your hand.
Crossbar pads wrap around your crossbars and allow you to safely transport gear on your roof rack without a standard carrier.
You will need four straps if you also choose to use them for the bow and stern tie downs.
The type you use will likely depend on your vehicle and your personal preference but it can be useful to have crossbars to secure your kayak.
Make sure the foam pads are secure.
Then slide each strap so that the buckle lays against the hull of the kayak.
Load the canoe onto your crossbars.
Tie the straps down with cam buckles to secure the kayak.
To install wrap the pads around your crossbars and secure in place.
Ensure the straps are laying flat against the kayak and that they are not crossed.
To tie down a kayak place it right side up on your roof rack and center it.
Tie down straps straps with cam buckles can be ideal for this as they have a secure buckle for tightening without needing to tie knots.