Crossbars span the width between two opposed vertical attachment bars in a half-width electronics rack or cabinet of accommodating height to enable vertical mounting of full-width electronics module in the half-width electronics rack or cabinet. The crossbars are used in opposed spaced-apart pairs with the full-width electronics module mounted vertically between the crossbars. Each crossbar includes a flat elongated main bar having five sets of three holes in a linear array, with the holes sized and spaced apart in accordance with industry standards for electronics racks. An attachment flange with a fastener opening extends from each end of the main bar and is delineated from the main bar by a notch. Between the notches, the same edge extends in a right-angle bend which further extends into a flange. Crossbars are provided in pairs, with or without packaging, racks, cabinets, and electronics modules.