Operating System (In the context of an actual map, OS stands for Ordnance Survey, the national mapping agency for Great Britain.)
On an OS map, it's a Public House
what does a bridge look like on a map
it means boo boo
Milestone
Post Office
a red line
Place of Worship
red is a road and the blocks are little houses
In the United Kingdom, a Government body, The Ordnance Survey (OS), surveys and prints maps of the UK at various scales.
A plus sign on an OS map signifies a church without a spire or tower.
They would look on the Map's key and the compass rose.