Thanks for the explanation. I dont know much about refereeing, this back/front referee thing is something i hear for the first time ever... and it is interesting to know.
As an Avs fan, i was obviously unhappy yesterday, when it happened, but naturally i dont think it was on purpose. And luckily it was not a super important game, like play-off one or whatever.
I can talk more about it if you're interested, but if not, feel free to ignore this post as it might be a little bit long-winded.
In the four-official system (two referees, two linesmen), here follows the basic approximate positioning of the four officials when the play is in one of the zones. I should also mention that I was taught the USA Hockey system, and the NHL system is based more on the Hockey Canada system, which is slightly different, but they're more or less pretty similar either way.
Front referee: positioned near one of the corners of the ice, generally not too far from the goal line. If the puck is on the near side of the ice, he will generally be as close to the boards as possible for the best view he can get in order to watch the play around where the puck is. He may be below the goal line if the puck is above the goal line, and if the puck moves close to the goal line, his options are to retreat closer to the net, or make a move around where the puck is by skating towards the net and pivoting around in order to get "above" the puck. If he's "above" the puck and the puck gets passed up to the point, he will do the reverse and pivot around the players who were on the side boards in order to get back towards the corner. If the puck gets close to the net, he'll skate towards the net in order to both get a better view of any potential infractions in a goal mouth scramble, to see if the goalie covers the puck, or if a goal is scored (but with video review in the NHL, this last one is slightly less important). When the puck is on the far side of the ice, he'll be positioned near the goal line, again watching the play around where the puck is, moving closer to or further away from the end boards so the net doesn't block his view of the play. There's more to it than that, but that's a rough description of what he does.
Back referee: positioned in the neutral zone on the opposite side of the ice as the front referee. Mostly watches behind the play, but can occasionally catch something that happens. Occasionally the front referee will be on the end boards with the puck in the corner, and will retreat behind the net in order to switch sides of the ice. The back referee will then also switch sides of the ice. However, in USA Hockey at least, you're very, very heavily discouraged from going behind the net to switch sides, but I see NHL referees do it more often. The reason for the discouragement is that USA Hockey officials will also often work the three-official system with only one referee (but still two linesmen), and they don't want you to get into that habit since when you're in the three-official system you don't want to be in the middle of going behind the net only to have the play suddenly go the other way and be stuck way behind the play.
Front linesman: almost right on the blue line. Retreats here after dropping the puck for a faceoff. Holds the line in order to make calls on whether the point man keeps the zone or to determine if the puck has exited the zone. In the NHL, he will often verbally yell out when the puck has exited the zone, but when I worked as a linesman, most of us didn't.
Back linesman: positioned in the neutral zone, a little bit inside the red line, on the opposite side of the ice as the front linesman. When you're the back linesman you don't really have a lot on your plate, so not much to say here. Sometimes the front linesman has the play come up near the blue line on his side of the ice, forcing him out into the neutral zone, so the back linesman will get closer to the blue line in order to get a better view of whether the puck gets held in the zone or exits the zone. Occasionally you'll see the linesmen do a front/back switch as a result of this happening.
Another thing that linesmen do is that when the puck is blown dead, usually as a result of the goalie covering the puck, they'll both skate into the zone towards the net (and sometimes very quickly depending on what's happening) in order to discourage or break up any rough stuff. That's actually a large part of the reason for having linesmen; they're kind of like bouncers on the ice. That's why you see a lot of linesmen who are big and tall, since it's their job to discourage and break up altercations. Referees sit back and watch for what to call when an altercation, post-whistle scrum, fight, etc. break out, and will only physically intervene if something imminently very dangerous is about to happen, such as, say, a goalie covering the puck, having his mask fall off, and an opposing player trying to start punching him in the face before the linesmen can skate in to do their thing.
When the play goes the other way, everything reverses: front becomes back, and back becomes front. The back linesman hustles towards the blue line to make (or not make) the offside call on the zone entry, becoming the front linesman in the process. Ideally the former back (and now front) referee will already be in the zone. The former front (now back) referee and linesman don't usually have a reason to hustle into place.
That's a very basic rundown of what the four officials do when the play is in the zone, such as the power play Colorado was on right before the incident that this thread is about. There's much more to it, such as what they do when the puck is dead, in the neutral zone, and so on, to the point that USA Hockey makes supplemental officiating manuals covering this stuff, and they can be quite long depending on the level they're aimed at.
If you read this whole post, then I commend you. I feel like I've written enough about it at this point.
