Football fans are just realising what the 'D' on the edge of the penalty area is for and its real name

With so much football to watch these days, you would presume that passionate fans of the sport would know all of its rules. But there are some laws that even experienced supporters may not know.

While having a full understanding of offside, for example, is crucial to enjoying a match, other rules have less of an impact on a typical game and can be easily overlooked.

One particular law which has stumped some football supporters is the presence of the 'D' outside of the penalty area and what its exact purpose is for.

While some fans are unsure why it is marked on the pitch, almost all supporters will have been using its incorrect name.

Instead of being called the 'D', the correct terminology for the line is the penalty arc – which gives a hint to its purpose.

Just like for a free-kick outside of the area, opposition players must remain at least 10 yards from a penalty taker.

To ensure there is no encroachment, opposing players must stand behind the penalty arc in the process of a spot-kick being taken and may only move once the taker has made contact with the ball.

Regarding the process of a penalty being taken, the laws of the game on the International Football Association Board (IFAB) website state: "The players other than the kicker and goalkeeper must be: at least 9.15 m (10 yds) from the penalty mark, behind the penalty mark, inside the field of play and outside the penalty area."

There are a number of laws regarding the retaking of a penalty kick if encroachment occurs.

According to IFAB's Law 14, as reported by The Mirror, a penalty must be retaken if the attacking team encroaches and the ball finds the net, or alternatively both teams encroach regardless of the result.

A spot-kick is also retaken if the defending team encroaches but the penalty taker fails to find the back of the net.

Alternatively, if the penalty kick taker misses but there is encroachment by the attacking side, an indirect free-kick is awarded to the defending team.

So, now you know – if you didn't already.