move the chains

Short definition from Wiktionary

Verb

1. 1
   To alter the position of the device, a chain holding two sticks ten yards apart, used to initially determine the position of the line crossing which yields a first down for the offense, which may be moved by penalties or by the offense gaining a first down.
2. 2
   To convert a play that would result in said chains being moved.
3. 3
   To advance toward a goal.