(Mishnah): Kohanim guard in three places in the Beis ha'Mikdash -- in Beis Avtinas, Beis ha'Nitzutz, and Beis ha'Moked.

There were Aliyos (upper stories) in Beis Avtinas and Beis ha'Nitzutz. Rovim (young Kohanim) would guard there;

Beis ha'Moked was built like a dome. It was a big house, with stone Rovdim (this will be explained) jutting out all around. The elders of the Beis Av (the sub-division of Kohanim scheduled to serve the next day) would sleep there, with the keys to the Azarah in their hands;

Pirchei (young) Kohanim would sleep on the floor (Rosh - with pillows under their heads);

They would not sleep in Bigdei Kehunah. They would fold them under their heads and sleep in Chulin garments.