The circular cam surface 30 of the flange 27 of U plate 24 circles about screw 28 and extends or projects in one direction on one portion 30 of the circle and projects in the opposite direction in {HEAD ~ the opposing portion} 30 of {TAIL ~ the circle} 
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The circular cam surface 30 of the flange 27 of U plate 24 circles about screw 28 and extends or projects in one direction on one portion 30 of the circle and projects in the opposite direction in { HEAD ~ the opposing portion } 30 of { TAIL ~ the circle }
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