gain line

Short definition from Wiktionary

Noun

1. 1
   an imaginary line running across the pitch perpendicular to the touchline and passing through the breakdown or set piece. The subsequent phase is said to have passed "over the gain line" if the gain line at the subsequent breakdown is in front of the last, or "behind the gain line" if it is behind.
2. 2
   Alternative form of line to gain.