ASA Dead Ball Line

[noobie]

Hi folks. By way of introduction, I'm making a return to officiating (local Parks & Rec, SP) after a 19-year absence. A lot has changed ... and it seems I've forgotten more than I ever knew. This could make for a very long season

I was handed an ASA 2005 Rule Book, to which I'm supposed to conform, and see a phrase used in a few crucial places: "Dead ball line is considered in play" (example: Rule 1, "DEAD BALL" definition, C).

Can anybody interpret that for me? "Dead ball line" is defined nowhere. Does this mean the line separating foul territory from the out-of-play zone?

Thanks in advance!