Sometimes permanent fenders are already on the wharf or pontoon , and this makes life really easy for you as you don't need to use your boat's own fenders. However, sadly, that it often not the case.
So, if there's no protection, you'll need to use 3 or 4 fenders depending on the size of your yacht.
Many people make the mistake of evenly spacing the fenders out along the hull...
... but what you actually want to do is position them to protect the widest part of your yacht.
When using fenders, tie them to the guard rail using a clove hitch. This is important so that you can tie and retie fenders quickly, yet the fender is still secure. See below for how to tie a clove hitch.
Depending on the height of the wharf or pontoon,the smartest thing to do if it's possible (to prevent too much strain on the guard rail) is to tie them to the bottomof a stanchion. This may not be possible, depending on where you need the fender to be the most effective, but it's worth considering each time you dock.
Generally if the bottom of the fender is just above the water line- or just grazing it - you'll be right for most floating pontoons. If it's a fixed wharf that's still a good way to begin, but once the wharf is in good sight, you'll need to estimate the height as you're coming in. If this means you are not ready, request the skipper to go round again to get the fenders in the right position - far better to do this than damaging your yacht's gel coat or paintwork.
Read more at http://www.sail-world.com/USA/Using-fenders-101:-The-smart-way/78989