Skateboard trucks attach the wheels to the skateboard deck. Each truck consists of a baseplate, a kingpin, a bushing, a hangar, and an axle. Trucks are usually made of alloy metals. Manufacturers are continually experimenting and manufactured different types of metals to try and improve the durability and performance of the trucks and at the same time making them light weight.
The baseplate is the foundation of the skateboard truck. It is bolted to the board and is attached to the hangar. Skateboard trucks typically have a standard pattern of four mounting holes to fit the majority of skateboard decks. The kingpin is a large bolt that is mounted into the bottom of the baseplate and secures the axle and hangar to the foundation of the truck. The kingpin can be adjusted to allow more or less maneuverability.
Bushings give the skateboard truck its pivoting ability allowing the board to turn. They are available in different degrees of hardness that affect the overall turning ability of the skateboard.
The hangar is the part of the truck that interlocks the axle with the bushings and kingpin.
The axle is the longest part of the skate truck. Wheels, with bearings already inside, are securely attached on each end of the axle with threaded bolts. The axle is the part of the truck that is used to grind. When you buy a skateboard, you want to make sure the axle is no wider that the width of your deck.