Palnuts are a "locking device" for nuts made of stamped sheet metal. They are screwed onto the stud or bolt on top of an ordinary nut. The palnut has a series of protruding barbs that lock the nut in place when the nut is tightened. This lot contains one each Pratt & Whitney PWA1608 Palnut Wrench plus 100 each Pratt & Whitney p/n: 7635 Palnuts in new surplus condition. Usage: Pratt & Whitney R-985, R-1340 and R-1830 radial engines. This special tool is very handy when removing or installing palnuts. They are 3/8"- 24. The wrench might have writing on it.