Trucks are needed to make the suspension for the skateboard and to steer. Without trucks a skateboard would be a snowboard. Some skateboards have soft suspension e.g a longboard, but some have hard e.g trick skateboards. Some trucks are made of plastic, like these ones, but most trucks are made of metal or even carbon fibre. They are made of carbon fibre, because it is light and flexible so it doesn't snap.The metal used in most trucks is aluminium to shed weight but to increase strength.www.dropthroughlongboard.com
The deck is the most important part of the skateboard. It I the backbone of the board. It has a flick at the end so you can do tricks and to rest your feet. They are normally made of wood, but some boards are made of carbon fibre. Wood is a good substance to use because it is flexible and light. However it rots. Carbon fibre is also light and flexible but it is stronger. However it is more expensive than wood. The deck consists of lot of thin layers of wood so when they are packed together it makes a tight bond that is very strong. The wood they use in the deck is most commonly maplem.youtube.comDiscovery / Science Channel's "How It's Made" Skateboard episode
The bolts are made from something called steel wire rod. The bolts are here to squeeze the board so it is stable.https://m.youtube.com/watch?v=3kxcw08p_oYwww.thomasnet.comThe bolt is a crucial component in modern manufacturing and has a vast range of applications in both commercial and industrial products, from airliners to gardening tools.
The wheels are made from a special type of rubber called polyurethane. They are made from this because it is very easy to form in to a wheel shape and it creates a lot of grip.