Dado
Affiliate link — we may earn a commissionA dado is a flat-bottomed groove cut across the grain of a board. It's sized to accept another board's thickness, creating a strong shelf or divider joint. You cut dados on a table saw using a stacked dado blade set (two outer blades with chippers in between) or by making multiple passes with a standard blade. Common widths are 1/4-inch, 1/2-inch, and 3/4-inch to match standard plywood and lumber thicknesses. Plywood labeled 3/4-inch actually measures about 23/32-inch, so test the fit before cutting a whole project's worth of dados.
Why It Matters
Dados are the backbone of cabinet and bookshelf construction. A shelf sitting in a dado carries more weight and resists racking better than a shelf held with screws or dowels alone. The groove distributes the load across the full width of the joint instead of concentrating it at fastener points.