When open, a keyboard having {HEAD ~ keys} that are apportioned between the housing and {TAIL ~ the base} is accessible 
are apportioned between
When open , a keyboard having { HEAD ~ keys } that are apportioned between the housing and { TAIL ~ the base } is accessible
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH REL REL REL OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH