[BoomerSooner]

Probably the best way I've ever had the IW explained to me is this...(assuming ball in possession no fumbles, no pass in the air, nothing like that)...The team in possesion has the choice of replaying the down or taking the play down where the whistle was blown.

So for example, 4th and 10 at the 50, A18 fakes a handoff to A28 who goes into the line and is tackled. R blows the whistle thinking A28 had the ball, but A18 is 10 yards down the field around the end. The linesman on that end should have picked up the QB with the ball and marked him down where he was at when the whistle was blown.

Now comes the decision for A, under normal circumstances, they would likely take the play resulting in a 1st and 10 at the B40. However as applied to this circumstance, 1st and 10 at B40 does nothing for them, because if the keep the play then the game is over...no replay of the down. However with any IW, the team in possesion is given the choice to replay the play regardless of the game situation (time, down, distance, score don't matter). So as time has expired A will likely want to replay the down so we go back 4th and 10 at the 50 with an untimed down since the clock expired on IW play.