Modular rack system with gussetless joints

A rack system for attaching equipment to a vehicle includes an elongate base plate having a top surface, a bottom surface configured to engage a top surface of a sidewall of the vehicle, and a first aperture through the top surface and the bottom surface. An elongate upright coupled to the elongate base plate includes a perimeter surface defining an interior space, a first support rib disposed in the interior space, and a first end comprising a first female threaded bore extending in a longitudinal direction within the interior space of the elongate upright. A first threaded fastener is disposed through the first aperture in the elongate base plate and coupled within the first female threaded bore of the first end of the elongate upright.