Rout a notch (width is half the thickness of wood, and depth is half the depth of wood) on each end of the wood used in the project along the top edge using a router equipped with a straight bit that is half the thickness of the wood used in the project.
Rout a notch (width is half the thickness of wood, and depth is half the depth of wood) along one edge of each hardwood board.
Make two 3/8-inch-long slots at approximately six inches and eight inches in from each end of the project in the center of the routed notch using a router and 1/4-inch straight bit.
Apply a bead of wood glue along the center six inches of each notched edge of the project. Place one hardwood board over each end of the project so that the notches fit together and form a flush surface. Allow the glue to dry for 24 hours.
Drive a wood screw through the center of each routed slot with a screw gun into the bottom of the hardwood boards on each end of the project. Use wood screws that are 1/4 inch shorter than the thickness of the wood used in the project.
Sand the top and bottom of the breadboard ends using fine-grit sandpaper. Always sand with the grain.