In football, free kicks occur when the referee believes a rule has been broken. If central enough and within 30 metres from the goal, the attacking team typically attempts a direct shot on goal. However, the goalkeeper routinely places a "wall" of defensive players in between the ball and the goal to complicate the kicker's task of shooting on target.
source https://techxplore.com/news/2020-12-football-wall-harder-free.html
