What is the football throwdown bag used for?

Answer 1

Spot of fumbled ball, punt's spot of first touching, emergency flag (if more than two fouls occur the order goes: flags, hats, throw down bags), in the NFL, spot of a field goal since a missed one goes to the spot of the kick.

Some people use it in HS to determine where the passer throws the ball from to ensure that A) QB not over line of scrimmage and B) if intentional grounding called, penalty marked from that spot.