A
sill plate or
sole plate in
construction and
architecture is the bottom horizontal member of a
wall or
building to which vertical members are attached. The word plate is typically omitted in America and carpenters speak simply of the "sill". Other names are ground plate, ground sill, groundsel, and mud sill. Sill plates are usually composed of
lumber but can be any material. The timber at the top of a wall is often called a top plate, pole plate,
wall plate or simply "the plate".