Which statement correctly describes a through dado and a blind dado?

• A. Through dado runs completely through the board; blind dado stops before the opposite edge; through is used for shelf supports and blind for partial-depth like a cabinet back.
• B. Both dados run completely through the board.
• C. A blind dado runs completely through the board.
• D. Both dados are used only for decorative purposes.

Answer: (A)

A through dado is a groove that goes completely through the thickness of the board, while a blind dado stops short of the far edge. This difference matters because it determines whether the slot is visible on the opposite face and how the joint carries load. A through dado is ideal for shelf supports because the shelf can sit securely in the groove and be supported from both sides, with the groove visible on both faces. A blind dado is used when you want the joint to be strong without exposing a groove on the far face—such as when the back or a portion of the cabinet is hidden or when you don’t want the groove to extend through to the other side. The other statements misstate one or both dados: one claims both go through, which isn’t true for blind dados; another says a blind dado runs completely through, which contradicts its definition; and saying they’re decorative ignores their mechanical purpose.