Abstract: An improved crane boom structure for telescopic boom sections. The conventional, generally rectangular cross-sectional shape is modified to provide central guiding of the boom sections to locate the bearing forces transmitted between sections at or near the neutral axis where bending stresses are minimal for greater load carrying capacity for a given boom weight. The boom side walls are provided with channel shaped projections, the top and bottom channel legs being located on either side of the neutral axis of the beam section, preferably symmetrical therewith. Bearing surfaces are interposed between top and bottom channel legs of contiguous boom sections.