Abstract: An adaptor for connecting a ground screw to an upright beam of a solar panel support assembly includes (a) a cylindrical connector having an open ground-screw receiving bottom end and a top end, the cylindrical connector having an inner circumferential surface with a diameter slightly larger than that of the ground screw and at least two sets of bolt holes, each set of bolt holes including at least three bolt holes uniformly distributed circumferentially about the cylindrical connector at an axial level, and the at least two sets of bolt holes being axially distanced from one another; (b) an intermediate plate having a top surface and a bottom surface fixed to the top end of the cylindrical connector; and (c) an upright beam connector fixed to the top surface of the intermediate plate and extending upward from the intermediate plate.