also: hash · hashes · inbounds lines
Two rows of short field marks that limit how close to a sideline the ball can be spotted for the next snap.
Hash marks are the two rows of short marks running the length of the field. The rulebooks call them inbounds lines. A play can end outside them, but the next snap is brought back to the nearer hash instead of starting next to the sideline.
That spot creates field and boundary. The side across the field has more room, while the side next to the hash has less. Moving the hashes closer together reduces that difference; moving them farther apart makes it a larger part of play calling and defensive alignment.
hashes, inbounds linesthe numbers, yard lineCoaches also use hash as a ball-location call: left hash, right hash or middle. In that usage the word names where the ball is, not the painted mark by itself.
The spacing changes by level. NFHS high-school hashes are 53 feet 4 inches from each sideline, NCAA hashes are 60 feet from each sideline, and NFL hashes are 70 feet 9 inches from each sideline. The wider high-school and college spacing creates a larger field-boundary difference than the NFL spacing.