A subbase is a layer of material placed beneath a road, pavement, or foundation to provide support and stability. It typically consists of crushed stone, gravel, or other aggregates that help distribute loads and prevent settling. The subbase is crucial for ensuring the longevity and durability of the surface layer, such as asphalt or concrete. In construction, the subbase acts as a drainage layer, allowing water to flow away from the surface and reducing the risk of damage from moisture. Proper installation of the subbase is essential for maintaining the integrity of structures like roads, parking lots, and sidewalks.