Here’s the inner workings of a couple of my  3/8″ drive ratchets. 3/8 inch drive refers to the size of the part of the ratchet that accepts socket wrenches. Imagine an industrialized nation without ratchets and interchangeable socket wrenches. A Google patent search reveals dozens of designs over the last hundred plus yrs.  The two pictured have both seen heavy use and despite being 40 to 65 yrs old they are still ready for plenty more service. As of this writing both mfg’s (Snap-On Tools Corporation and Proto Tools ) are still in existence and spare parts are available.