A ratchet wrench including two ratchet wheels rotatably disposed in the ends of a housing, a pawl pivotally disposed for engagement with the ratchet wheels, a knob rotatably disposed in the middle portion of the housing and extended outwards of the housing so that the knob can be rotated from outside...http://www.google.es/patents/US5144869?utm_source=gb-gplus-sharePatente US5144869 - Control device for ratchet wrenches
