Folks, knotting to the life lines is fine but it should be around the stantion. Otherwise the normal movement of the boat can "walk" the fender out of place. Listen to Bjones, I use a brass snap clip attached to my toe rail at the dock. Perfect fit every time and the fenders don't move even when I have a sometimes "unseaman like" dock landing (it happens). When I raft I clip the same fender to the lower life line around the stantion, hull protected, no problem. I use cheap alumium caribiners for my spare fenders, $.99 at HD. In fact I have a bunch of them on board and use them for all sorts of things.