A pavement marker has a base having at least one opening formed therein. A groove is formed in the base substantially adjacent the opening. The pavement marker further includes a cover for covering the opening in the base. The cover is formed with at least one energy-directing rib configured for nesting with the groove in the base. The cover is ultrasonically welded to the base so that the energy directing rib melts and integrally fuses to portions of the base adjacent the groove.