There are a number of factors to consider when deciding what you should fasten your boards down with. Keeping them securely fastened in the long term and damaging the boards as little as possible during installation should be top priorities, but maintenance should not be overlooked. All your fastenings should be waterproof to avoid corrosion, so you will want to use a minimum of hot-dip galvanised steel. Here’s how some of the various attachment methods stack up.
Nails – The most basic way to secure two boards together is with a nail. Nails are cheap, plentiful and tools like nail guns have made tasks like fastening boards an absolute breeze. Nails are also easy to seal over, so keeping them watertight is not usually a problem. The downside to using nails is that if you ever need to pull the board up again, it is hard to do so without causing damage to the board. When nailing wood that's vulnerable to splintering, you should pre-drill the holes to avoid damage.
Screws – Screws are more expensive than nails and take a little longer to install, but have the distinct advantage of being removable. Screws can and should be countersunk into the deck so that they don’t jut up and rip half of someone’s foot off. This can be a slight disadvantage though, as it can allow moisture to pool and grime and mould to accumulate.
Tongue and groove systems – These types of decking boards don’t require any fastenings at all, they are specially designed to clip together. This obviously circumvents any of the issues faced by using screws or nails, but can cause issues of its own, such as inadequate water drainage. Having the boards clip together means that unless it's been engineered for, it's difficult for water to pass through which can cause pooling and dirt issues.
Proprietary screws and hidden fastening systems – Certain proprietary decking and fastening systems take a different approach to fastening a board to a deck, and use various means to fasten the boards in ways that make the screws or fasteners invisible. If you're looking at proprietary systems with invisible fastenings, consider whether or not boards can be easily replaced, and whether or not special boards are required to support the particular fastening system you've chosen.