{TAIL ~ The slider} has a contact portion in close contact with {HEAD ~ the inner peripheral wall} and positioned upstream of the block member at the first position in the sliding direction 
{ TAIL ~ The slider } has a contact portion in close contact with { HEAD ~ the inner peripheral wall } and positioned upstream of the block member at the first position in the sliding direction
TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH