A box-spring consists of a rigid frame containing extra-heavy-duty springs. This foundation contributes to softer support and a bouncier mattress. Because box-springs can allow mattresses to sag, many manufacturers add high-density block foam underneath the coils or provide a rigid foundation instead.
A traditional wood foundation is usually made of softwood, such as pine, or hardwood, it exist in different height sizes. It increases the feeling of firmness and stability.
A grid foundation is a combination of steel and wood.