Football pitch markings and design are required to meet strict regulations on exact measurements and placings depending on national and international guidelines.
At the highest level of football, clubs will consistently look for 'marginal gains', based on their ability to be flexible within the tight rules, to gain a potential advantage.
There have been some famous Premier League examples of clubs pinching a metre or two in their pitch dimensions to allow for more expansive tactics or more direct approaches, particularly for throw ins and corners.
However, certain rules remain set in place, which cannot be changed, including the presence of a line 'D' shape on the edge of both penalty areas at each end of the pitch.
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What is the Penalty box D used for?
Every football pitch will feature two 'D' shaped white line crescents on the edge of both penalty areas as a point of reference for players and match officials.
The distance of the penalty area is 18 yards (16.45m) from the goal line to the edge of area with the penalty spot measured at 12 yards (10.9m) from the goal line.
The 'D' is in place so the referee can accurately ensure all players – excluding the penalty taker and the goalkeeper – are 10 yards (9.1m) away from the penalty spot when a kick if being taken.
The radius of the curved 'D' is 10 yards (9.1m) and provides a line for the referee to work from to assess if players are 'encroaching' unfairly on a kick being taken.
The shape of the 'D' is curved to ensure each point is the required distance away from the penalty spot.
How are penalties and free kicks awarded?
If a player is fouled inside the 'D' a free kick is awarded, as the 'D' is not part of the penalty area, and is only used in the example above during a penalty kick being taken.
Fouls that are committed on the lines of the penalty area, excluding the 'D', are classed as penalty fouls, as the line forms part of the area.
In the example of fouls being committed elsewhere on the pitch, free kicks are generally awarded, with the referee selecting between direct and indirect free kicks.
Direct free kicks allow the taker the option to shoot directly and score with indirect free kicks requiring another player to touch the ball before it enters the goal to be counted as a legitimate goal.
