A sidewall of a trailer includes a side panel, an outer member, a base rail. The side panel is positioned within the channel. The outer member has a planar inner surface. The base rail has an upper portion offset from a lower portion. An outer surface of the upper portion of the base rail is generally parallel to and spaced from the inner surface of the outer member. A channel is defined by an outer surface of the upper portion of the base rail and the inner surface of the outer member. The side panel is positioned within the channel. The lower portion of the base rail is positioned beneath the channel.