The present technology relates to beams having a cross section defining a plurality of channels and assemblies comprising the beams. In embodiments the cross section may define four channels, facing in four directions. The cross section has the advantages of providing structural channels that provide strength, platforms for attaching sliding and fastening components, and conduits for protecting internal components. The interior and exterior surfaces of the channels are configured to permit multiple carriers to slide/roll in linear motion independently in multiple directions, with smooth action and stability due to one or more guiding features to distribute load. These and other embodiments are discussed in greater detail in the detailed description and drawing figures.