Utah HC mailbag: How do line changes work in hockey?

Last week, I asked the new hockey fans on X for questions about hockey. I got lots of responses, so I can’t promise to answer every question — but I’ll do my best.
This is the second part in this series. See part one, which talked about penalties, here.
Today, let’s talk about line changes. If you’re more familiar with other sports, you might call them substitutions, but in hockey we call them line changes.
You probably already know that each team is allowed to have five skaters and a goalie on the ice at a time. But you’ve probably also realized that there are almost four times as many players sitting on the bench as there are on the ice.
This is because hockey is a tiring sport. Even the best players in the world rarely average more than 25 minutes of playing time per game, and the average shift length usually falls between 45 seconds and a minute.
Because there are so many players on each team, everyone can give 100% effort at all times. This makes for high-octane hockey and a lot of excitement.
The only time a player is not allowed to leave the ice is when his team gets called for icing. The faceoff happens in that team’s defensive zone and the tired players are forced to participate, which often leads them to be trapped in their own zone.
Aside from after an icing, a player can change during or after any play.
You may have noticed players leaving the ice while play is happening. This is called “changing on the fly” and happens during virtually every play. It can be slightly risky because while you’re changing, the puck might end up in your zone, causing the oncoming player to have to rush to get back into the play — but it’s usually not an issue.
While changing on the fly, players must be acutely aware of their teammates’ positioning, as well as the positioning of the puck. If they get it wrong, they can end up with an extra player, resulting in a penalty for too many men.
The rulebook states that the player going on the ice can do so when the player coming off the ice is within 5 feet of the bench. If he joins before that and either he or the player leaving the ice have any impact on the play, it’s too many men.
You may have also noticed that players often jump over the boards, rather than going through the gate. This is because it’s easy for traffic jams to occur at the gate, which can result in either a too many men penalty or the oncoming player not being able to join the play quickly enough.
At the professional level, the player going on typically jumps the boards and the player coming off usually goes through the gate.
One of the biggest jobs of an NHL coach is to match lines. What does that mean?
Teams generally sort their players from best to worst in groups called “lines.” As a rule of thumb, the first line typically has the three best forwards on the team, the second line has the third, fourth and fifth best forwards and so on.
The top two lines usually play a lot more than the bottom two lines because they’re better. But you never want your bottom line to be on the ice with the other team’s top line.
The coaches look for opportunities to sneak their top lines onto the ice against the other team’s bottom lines, though it’s usually countered as quickly as possible by the other coach.
Remember when we talked about players getting stuck on the ice after an icing? That’s often when line matching is most effective because one team’s bottom line might be tired and stuck on the ice while the other team’s fully rested top line can go out and take advantage of the situation.
At various points throughout a game, you’ll see a goalie suddenly dart from his net to the bench. This is a strategy known as “pulling the goalie.”
Teams are allowed to have six players on the ice, which usually takes the form of five skaters and a goalie. But at certain points in the game, it makes more sense for a team to have six skaters, so they replace the goalie.
One situation in which the goalie gets pulled is during a delayed penalty. The referee will blow the whistle as soon as the other team touches the puck, so teams use that to their advantage by replacing the goalie with an extra skater in an attempt to score.
The other situation where the goalie comes out of the net is when a team is losing late in the game by a narrow margin. If you’re going to lose anyway, another goal against does not affect you. It’s better to have the extra skater to try to tie the game.
Pulling the goalie late in the game seldom pays off. But when it does, there’s nothing more exciting. Just ask Vancouver Canucks fans.
To answer the question that you now undoubtedly have, no: You can’t replace one of your skaters with an extra goalie, though that would be epic.