One of these devices “flashing” between tilted flat and sawtooth potentials exhibits Parrondo’s paradox, in which alternating two losing strategies eventually wins. These devices name the effect where directed transport arises in driven, asymmetric periodic potentials, making them useful models for molecular motors. A 1962 lecture updated a thought experiment in which one of these devices in a heat bath is connected to a paddle wheel in a different heat bath. That one of these devices appears to violate the second law of (10[1])thermodynamics, but doesn’t actually rotate because thermal fluctuations also affect the pawl and cause the gear to slip. Socket wrenches are alternatively named for these mechanisms. For 10 points, Feynman popularized a “Brownian” example of what mechanisms that only allow motion in one direction? ■END■