In the past, the tribologlcal behavior of sliding surfaces was explained In terns of adhesion at the sliding Interface However, It has been shown recently that plowing by wear particles at the sliding interface, which depends on the relative hardness of materials, has a significant effect on friction and wear properties. In order to demonstrate the effect of plowing, a checkerboard type undulated surface was created to eliminate the wear particles from the sliding interface by trapping them in cavities. The friction force and the wear rate of the materials with undulated surfaces are considerably less than those of the same materials without undulations. The frictional behavior of these undulated surfaces without any boundary lubricants was as good as that of well lubricated flat surfaces. Even good boundary lubricants cannot lower the friction coefficients of undulated surfaces further. Experimental results on surfaces coated with hard layers and slid with boundary lubricants are also reported.