{TAIL ~ An oil repellent layer} is applied to either the surface portion having grooves thereon or its opposing surface in {HEAD ~ the vicinity} of the narrower gap 
{ TAIL ~ An oil repellent layer } is applied to either the surface portion having grooves thereon or its opposing surface in { HEAD ~ the vicinity } of the narrower gap
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 OTH OTH OTH OTH