Football Live Ball
The ball is live when the down begins.
Line of Scrimmage
Players from both teams line up on the scrimmage line.
Football Snap
Before the play clock goes to 0:00, the offense must snap the ball to begin the down. A snap is a backward pass throw the legs from the center to the quarterback (both are players on the offense). Scrimmage downs always begin with a snap, also known as a hike.
The ball is live when the snap is made.
Football Dead Ball
A dead ball in football is when the down officially ends. Scrimmage downs end for the following reasons:
- A score is made
- A pass is incomplete
- The ball carrier is tackled to the ground
- The ball is carried or thrown out of bounds
Football Chain Crew
At the end of every down a group of referees called the chain crew mark the scrimmage line, first down line, and the distance between the two lines on the field.