Does the FED rulebook or casebook define "unnocupied and occupied bases"

[aevans410]

(continued from topic title) in terms of a balk? I had a coach question what an occupied base was, but couldn't cite a rules reference. I looked last night, but either overlooked it (most likely, my kids were unruly last night, or it doesn't exist. Any help would be appreciated.

Thanks in advance.