Final answer:
A three-line violation in indoor soccer or futsal results in a free kick for the opposing team from where the ball crossed the second line.
Step-by-step explanation:
The term three-line violation typically refers to a rule found in indoor soccer or futsal, where a player may not kick the ball across three lines (such as in a very long pass or a goal kick) without it touching the ground, a player, or the wall. When this happens, the opposing team is awarded a free kick. The free kick is taken from the spot where the ball crosses the second line. This rule is in place to discourage long balls and encourage more controlled, short-passing play.