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.
... population is spread out with 29.0% under the age of 18, 5.0% from 18 to 24, 29.0% from 25 to 44, 24.2% from 45 to 64, and 12.7% who are 65 years of age or older. Th ...