The first advancing seat is provided with a slide block capable of sliding along the first advancing seat in a direction perpendicular the front surface of the base, whereas {TAIL ~ the horizontal advancing seat} is mounted on the slide block of the first advancing seat and is provided with {HEAD ~ a slide block} capable of sliding along the second advancing seat in a direction parallel to the front surface of the base 
The first advancing seat is provided with a slide block capable of sliding along the first advancing seat in a direction perpendicular the front surface of the base , whereas { TAIL ~ the horizontal advancing seat } is mounted on the slide block of the first advancing seat and is provided with { HEAD ~ a slide block } capable of sliding along the second advancing seat in a direction parallel to the front surface of the base
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 TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH