What the 'D' on the edge of the penalty area is actually used for in football and its real name will surprise fans

The use of the abbreviation 'D' is commonly used by fans to refer to the edge of penalty area in football - but it actually has a completely different real name and usage.

In the early years of football across the world, teams would play with just two penalty boxes, and no markings to show the section outside the penalty area.

And while most teams now play with a pitch dimension of around 105 x 63, that wasn't the case in the late 1800s,

with some pitches even reaching 200 yards long and 100 yards wide before FIFA outlawed that by introducing a specific stipulation. They also brought in the halfway line and centre circle.

The definition of the area outside the penalty box was better clarified in 1937 when the 'arc' - now commonly known as the 'D' was brought into the sport, in order to mark the part of the pitch outside the penalty area which is closer to the 12-yard spot than 10 yards.

But it also has a second meaning which fans may not be aware of.

The 'D' covers the 10 yards in which players are not allowed to encroach into when a penalty kick is being taken.

Should encroachment by the opposition team - or the team who were awarded the penalty kick - occur, then the referee has to force the penalty to be retaken with no change to the scoreline.

The International Football Association Board (IFAB) set the rules and regulations of football worldwide.

Their definition of the restriction is as follows: "The players other than the kicker and the goalkeeper must be: at least 9.15 [metres] (10 yds) from the penalty mark, behind the penalty mark, inside the field of play and outside the penalty area."

If a defensive player encroaches the penalty area but the penalty is not scored, meanwhile, there is also a mandatory re-take of the spot kick.

The rule, though, is marginally different in a specific case of encroachment by the attacking team.

If one or more players illegally enters the restricted zone as the spot kick is being taken, and the player misses, an indirect free-kick is awarded to the defensive team.