 Let's look at how a play in American football will end, and more specifically what constitutes a tackle in American football. This is a key concept to understand because, except for a few cases like a team scoring or an incomplete pass, pretty much every other offensive play that you see throughout a game will end in one of these ways. Each time that a play ends, wherever the ball is when that player goes down, will become the line of scrimmage for the next play. We'll also look at a few ways how a player can go down voluntarily and why they may want to do that. So all that said, we're going to look at five different ways to end a play, but as we'll see 98% of the time it's going to be one of the first three. The first way is the most common. This is when a player is down by contact. This means that a defensive player has touched the ball carrier in some way and then subsequently some part of the ball carrier's body other than his hands or his feet makes contact with the ground. So this is probably what you picture in your head when you're thinking about tackling in football or rugby. Basically it's one guy trying to pull down the guy with the ball while he in turn is trying to stay on his feet for as long as he can. Usually this will mean that the defensive player will give the ball carrier a big bear hug and haul him to the ground, but he could also push him hard enough that it would make the ball carrier lose its balance and fall over. One final point to make on this is that the defensive player's contact does not necessarily have to be the cause of the ball carriers falling over. So even if a player with the ball loses his balance without touching anyone, maybe he's trying to jump or spin around the defender and on the way by the defender's fingernail likely grazes the ball carrier's forearm and then the guy with the ball falls down just because he's lost his balance on his own, that still counts as being down by contact because there was contact and now the ball carrier is down. The second way is stopping a runner's forward progress, which is when one or more defenders manages to stop the ball carrier from moving forward anymore, either by standing in front of him or holding him back from behind. Once a player has the ball and is looking to run forward, because of what we just looked at, one of their main goals is not to go down and lots of players will get good at maintaining their balance no matter how hard the defense tries to pull them down. So rather than force defending players to resort to perhaps trying to pick up a ball carrier and body slamming him on the ground, the rules just say, look, if you can stop a guy moving forward for a few seconds, that's good enough. We don't want anybody to get hurt except for, you know, concussions. So the ref can blow his whistle and stop the play because forward progress has stopped. You may also hear forward progress discussed as to where the ball will be placed for the next play. So if a player with the ball runs forward, say, to the ten yard line and a defensive player hits him there and pushes him back five yards where he falls over, because he made it to the ten, that's where the ball will be placed because that's where the contact began. You might hear the announcer say something like forward progress took him to the ten yard line. On the other hand, if he runs to the ten and then turns around on his own and tries to run across the field, goes back five yards in the process and then gets tackled, then that ball will be placed at the fifteen. So while it is not tackling in the traditional sense, when a ball carrier goes out of bounds, the result is the same as if he had been tackled at that spot. So wherever the ball is when he steps out of bounds, will become the next line of scrimmage. If the player is along the sidelines for a defensive player, shoving the ball carrier out will obviously be easier than tackling him. But if it's late in a half, the ball carrier may decide to go out of bounds on purpose in order to stop the clock. So if a player goes down close to the sidelines, the referee will signal to the guy running the clock whether or not he went out of bounds. So if he stays in, the rep will wind his arm like a windmill, which is the signal to keep the clock running. Or if he went out, then he will do a shoving motion as an homage to Frank Underwood and that one ridiculous scene of House of Cards. The final two ways of ending a play are the other ways of doing so voluntarily. The first is if the runner slides feet first. If a player does this, it's almost always going to be the quarterback. So while running backs and wide receivers will do everything they can to avoid going down no matter how many defenders hit them, quarterbacks will usually avoid contact if they can. So for example, if there are five yards to go for the first down and the quarterback manages to run six, and he sees a few defenders waiting for him ahead, he's probably going to do the smart thing and give himself up and slide down so he doesn't get hit very hard by one of them. This might also happen late in a game if there's a turnover rather than trying to say return an interception for a touchdown and risk another fumble. A defensive back might slide down so that his offense can come out and just kneel the ball to kill the clock, which is a fantastic transition to our final way that we'll look at, which is kneeling the ball to kill the clock. This is when the quarterback will receive the snap from the center and he just kneels down on one knee, or as it is sometimes called, taking a knee. This will happen usually late in a game when a winning team wants to just run the clock out because when you kneel, it's basically you're going down and bound, so the clock will keep ticking away. So there you have it, five ways that a play can end. A traditional down by contact tackle, stopping forward progress, going out of bounds, either voluntarily or not, sliding and taking a knee. And it's in one of those ways that almost every play will end.