Unirails are integrated structural components combining ladder frame and unibody characteristics, typically utilized in light-duty truck and van chassis. These heavy-gauge steel rails run longitudinally, providing primary load-bearing support for powertrain, suspension, and body attachment. Key features include integrated hardpoints for direct mounting of body and chassis components, reducing the need for traditional crossmembers. Manufacturing utilizes closed-section profiles for maximized bending and torsional rigidity. Variations exist in rail height, wall thickness, and cross-sectional shape based on vehicle GVWR and intended application. Replacement necessitates precise alignment and welding to maintain structural integrity.