A straight edge bar clamp spreader comprises a straight edge bar, an inner channel portion, parallel channel portions, and two-way bosses or divots, a clamp, and a clamp-spreader. The inner channel portion is provided along an elongated central region of the bottom surface of the straight edge bar with a constant cross-section. The parallel channel portions are provided along two elongated parallel regions of the top surface of the straight edge bar. The two-way bosses or divots are provided across and on an inner surface of the inner channel portion of the bottom surface and an outer surface of the top surface and configured to define the predetermined stopping positions for two-way movements along the bottom surface or the top surface. The clamp is installed in the inner channel portion of the bottom surface. The clamp-spreader is installed in the pair of parallel channel portions of the top surface.