{HEAD ~ The upper inside surface} and the lower inside surface of the housing define {TAIL ~ a group} of slots 
define
{ HEAD ~ The upper inside surface } and the lower inside surface of the housing define { TAIL ~ a group } of slots
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH