Previous spot fouls should be enforced, not just from the previously yardline, but the actual spot on that yardline where the ball was last snapped or kicked.

Tip for Umpires:
I purchased Honig's "slide" down indicator. It is a wrist band with numbers 1-4 on it and a plastic marker that slides across the strap. When I'm on the field I wear it on my left wrist, because there is no finger strap to interfere with my finger whistle. The 1 is the left hash, 2 is left upright, 3 is right upright and 4 is right hash. Adjusting the slide between numbers helps me keep 7 positions for the ball between the hash marks.

I previously use the normal "finger" down indicator, but had problems placing the strap on fingers with my whistle. I keep downs on my right wrist and ball position on my left.

Rick,

I too wear an indicator where the lateral position of the ball. Been doing so for 7 years now. Others around the province have adopted the mechanic.

Around pinky is one hash, index is the other. And configs for points between also.

REPLY: Maybe it wasn't clear in the prior posts, but that's true for all enforcements: Previous spot, spot of the foul, spot where he run ends, succeeding spot. All are measured from spots, not simply the yardline.

Bob, agreed. Many umpires (officials) either don't understand that, or are too lazy to move to the exact enforcement spot. For many, just being on the correct yardline is good enough.

Since officials love to be a bit uptight about wording and things... Not ALL enforcement is from a spot instead of a yardline. When a free kick is involved (foul before the Kick, or a rekick), the team is allowed (oh - in NCAA at least) to select the position of placement of the ball on or behind the given yardline.
Normally placed in the center, but the kicking team can ask for it to be placed somewhere else.

REPLY: Yes...the same is true for Federation except for the "or behind" the given yardline part. That "behind" part doesn't exist in Fed ball. However, anytime that a team may choose the spot between the hashes to put the ball in play, that same choice remains after an enforced penalty if the down is replayed. I know that in NCAA ball, if there's a foul by A during a try and the down is replayed, A does not have the choice of where to replay the down from. That's established by the enforcement of the penalty, right?

(ncaa) That's correct Bob. Team-A can only choose where to snap again on a TRY if the foul was on team-B

Under Fed rules the foul is always enforced from a spot determined by the play and the foul committed. If after enforcement team A still has an option to place the ball between the hash marks, then we'll honor their choice. Once placed, the new previous spot is determined for fouls committed during the next down.