How to Build Shelf Joints

Lay out each shelf's placement along the two sides. Make a small mark on one of the sides to indicate each shelf's bottom edge. Lay the two side boards next to each other on a flat surface. Line up the top and bottom edges. Use a level as a straight edge to draw a line across each side. These lines will be used as a guide line to cut the dado joint.

Position a flat-bottomed dado bit on your table saw according to the manufacturer's directions. Line up the first pencil line on a side board with the dado bit's edge. Slide the table saw's guide over until it rests tight against the side board's edge.

Slide the board across the dado bit, keeping the board pressed tight against the guide. Position the side board's second pencil line with the dado bit's edge and move the guide over so it is once again pressed against the side board's edge. Slide the board across the dado bit.

Cut along each pencil line the same way you cut across the first two. Set the first side board aside. Cut through the second board's pencil lines with the dado bit the same way you cut through the first board's lines. Line up the two boards side-by-side and check that each dado joint lines up.