re: I constructed this from an advertisement

Thank you both! I doweled and glued 3 1×6 boards together, 16 ft. long, 3 of them, to get the number of board feet required to do the project. I’d scaled up the dimensions from a little 3" by 1½" ad from the Sunday paper. Gave me an excellent opportunity to increase my clamp selection! I still had to create clamp ‘extensions’ by cutting convex (bowing-out) strips from 2×4′s, attaching ring bolts to them big enough to allow the clamp heads to go through, then clamping the extensions to pull tight the dowel joints.