{HEAD ~ The vertical advancing seat} is provided with a slide block capable of sliding along the vertical advancing seat in {TAIL ~ the vertical direction} relative to the base 
{ HEAD ~ The vertical advancing seat } is provided with a slide block capable of sliding along the vertical advancing seat in { TAIL ~ the vertical direction } relative to the base
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH