For one thing, it provides the lower anchor for the wall panels. Perhaps more importantly, it determines exactly how the panels relate to the foundation. To keep water and pests from entering the building at its base, the panels must extend below the outside of the slab. This can be accomplished in several ways, and different approaches work better in different situations, STEELBUILDING.COM's online design and pricing
system offers a number of different base options which are illustrated and described in detail below. We recommend that the first three options -- base angle, base trim, and deluxe base trim -- be used with concrete slab foundations (option 3 is our favorite). The remaining three options -- base girt, base channel, and base channel with trim -- are designed for special circumstances.