A hole in the pivoting ball top extension accepts a pin, and the hole is situated with respect to the frame such that the pin will be against the frame when {HEAD ~ the pivoting ball support face} is in {TAIL ~ its first position} 
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A hole in the pivoting ball top extension accepts a pin , and the hole is situated with respect to the frame such that the pin will be against the frame when { HEAD ~ the pivoting ball support face } is in { TAIL ~ its first position }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL