means for adjusting the support and guide mechanism with respect to the power tool, said adjusting means operating to raise or lower the tool with respect to said support and guide mechanism to vary {HEAD ~ the extent} of {TAIL ~ operation} of said tool on the surface of the workpiece 
means for adjusting the support and guide mechanism with respect to the power tool , said adjusting means operating to raise or lower the tool with respect to said support and guide mechanism to vary { HEAD ~ the extent } of { TAIL ~ operation } of said tool on the surface of the workpiece
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