My dictionary says "nef" is "the nave of a church."
Anyway, I went on to look up "nave" and it said it was "the central part of a church, extending from the narthex to the chancel and flanked by aisles."
So I looked up "narthex" and "chancel"
"narthex" was said to be "a portico or lobby of an early Christian or Byzantine church or basilica, originally separated from the nave by a railing or screen" and "chancel" is "the space around the altar of a church for the clergy and sometimes the choir, often enclosed by a lattice or railing".
Basically, it's what I'm doing right now. NEF!