Under roundover bits, sometimes called round-under router bits, carve a smooth, rounded profile along the underside of solid surface materials, laminates, and wood. Unlike standard roundover bits that shape the top edge, under roundover bits soften sharp corners on the underside of the workpiece, protecting edges from chipping and providing a clean, decorative profile. This application is common in countertop fabrication, furniture trim, and cabinetry where the underside of the material is visible or subject to handling.