Abstract: An interlocking system for photovoltaic and other roof-mounted panels is disclosed. One use is for a photovoltaic module which comprises a photovoltaic laminate. The laminate has an upper side which faces the sun during normal operation, and a lower side. The module also comprises a base coupled to the lower side of the photovoltaic laminate. The base also has an outer perimeter and comprises a first engagement site and a second engagement site. The first engagement site comprises a first protrusion having a hemispherical surface, an opening extending through the hemispherical surface, and wherein the first protrusion extends in a first direction and the first direction is substantially perpendicular to the outer perimeter. The second engagement site comprises a second protrusion having a cylindrical surface, the protrusion extending in a second direction, and the second direction is substantially perpendicular to the outer perimeter.