Some ski cores also have some bumps and shapes on the top, which are usually seen in the shape of the deck. Using these ridges and shapes is another way to give your skis different properties like flex, stiffness or weight.
Most ski cores are made from laminated hardwood strips such as beech, birch, aspen, paulownia, fuma, ash, fir, maple, spruce, poplar, or bamboo, usually with layers of different wood strips pressed together. Wood is used because it gives a life-like feel while having good shock absorption, holding its shape well and having a fairly low resonance.