The lines are numbered along the edges of the map, and at ten grid-square intervals across the sheet. You can use these lines to pinpoint any location in Britain using a grid reference.

In order to pinpoint an exact spot on a map, you’ll need to know how to give a grid reference. Most large scale maps have numbers that run around the border, from left to right, and top to bottom.

Four-figure grid references are found as follows: First, write the eastings number of the bottom left corner of the square (eastings are found along the bottom of the map).

Plaques with map grid references have been attached to gates and stiles to help disorientated walkers find their way on Snowdon. The Snowdonia National Park said the idea came from mountain rescue ...

Map grid references of 250 homes in a rural part of north Wales have been detailed for householders to help direct emergency services during calls. It follows concerns by people living in the ...