The most common and easy way to glue two boards together (in order to make a wider board) is to joint the edges, apply adhesive and clamp them under pressure until the adhesive cures. Occasionally we will add biscuits or a splines in between the edges; in other cases, when we need to make a superior joint with greater contact surfaces between the two edges, we will use a special router or shaper bit to make a series of grooves and complimentary ridges that will fit into the grooves.
In the case of the table top I built, I choose a third technic. Few years ago I read a book on country furniture making, written and illustrated by George Buchanan: The Kitchen – Timeless Traditional Woodworking Projects. While reading this book I’v learned how to join boards without the assistance of clamps. A key is inserted into the edge of the two boards, than pegs are inserted into the boards to secure the keys. But the pegs have a much more important mission. As the holes in the keys and the boards are intentionally not in complete alignment, diving the peg into place will create a force to pull the two edges together (see illustration attached).
The hole in the key is off seted by a tiny amount – enough to make the peg spring and pull the key inside the mortise and consequently the edges tighter.
I made the keys from ash. At Lie Nielsen’s open house event I used mortising chisels to crated the mortises. Later on in my studio, I finished the remaining mortises by combining together the force of a cordless drill, a mortise chisel (for the mortise narrow edge) and a bench chisel on the long edges.