There was a place on the floor of the fire room, one cubit square (about 18”x18”), on which there was a marble slab with a ring fixed in it and a chain on which the courtyard keys were hung. When closing time arrived, the kohein would lift the slab by the ring and take the keys from the chain. He would then lock up from the inside while a Levi sat outside. (The text says “slept”; see Bartenura, et al.) When the kohein finished locking up, he would return the keys to the chain, place the slab back in place, lay his garments on top of it and go to sleep there. If one of the kohanim had a seminal emission, he would go down the winding staircase that passed under the Temple and which was lit on both sides until he reached the mikvah. Rabbi Eliezer ben Yaakov says that he would depart by the winding staircase that passed under the cheil (the area around the courtyard) and then depart through the Tadi gate.
The Temple mount was 500 cubits by 500 cubits (approximately 750’x750’). The largest part of it (i.e., the largest area outside of the courtyard) was on the south, the next largest on the east, followed by the north, with the smallest part on the west. The larger the area, the more it was used.