Each piece has a slot (the groove) cut all along one edge, and small outcrop (the tongue) on the opposite edge. Two or more pieces thus fit together.
... C. Pinckney[?] 14 Federalist Rufus King (14) Other elections: 1792, 1796, 1800, 1804, 1808, 1812, 1816 Source: U.S. Office of the Federal Register ...