Crossbars 312 and 314 located slightly inboard of sprockets 304 and 310 serve as limit stops for slider 302 at opposite ends of {HEAD ~ its path} of {TAIL ~ travel} 
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Crossbars 312 and 314 located slightly inboard of sprockets 304 and 310 serve as limit stops for slider 302 at opposite ends of { HEAD ~ its path } of { TAIL ~ travel }
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 REL TAIL TAIL TAIL TAIL TAIL