All skateboards have a concave. The concave is the curved shape of the board when viewed widthwise. A skateboard deck is rarely flat, it is always more or less concave.
The concave has 3 uses:
- to offer more control during tricks,
- to wedge the foot when riding,
- to improve the solidity of the board.
In general, there are 3 types of concave: weak, medium and strong. Depending on the brand, they can be named differently (Light or Mellow, Medium, High or Strong). It is very rare to find a completely flat board, except on the reissues of old-school boards.
It is important to know that the concave can be different on two boards, even if they are both rated "Medium". Indeed, each brand keeps its own manufacturing process and some skaters prefer certain brands for their particular concave.
If in doubt, for a first skate, it is better to choosea medium or light concave.