I know a former ABC maintenance engineer who was involved with Family Feud when it was at ABC. He explained how the FF main game board worked.
Each of the flaps on the main game board was attached to a piece of spring wire which effectively formed a coil spring. In the "unrevealed" position (answer not facing the audience) the flap was under constant tension from the coil spring. A solenoid with a retractable plunger kept the flap from turning and held it in the unrevealed position. To reveal an answer, the solenoid plunger was retracted, allowing the coil spring to unwind and rotate the flap into the "revealed" position.