LAST week Caroline Morgan asked readers if they knew what this sign meant.

Here is her letter and some of the replies that were sent in...


Can you identify this sign?

CAN any of your readers please help me identify what this sign means?

I have seen it on the Old Police Station in Knutsford, buildings in Manchester and a church in Alderley Edge.

I asked in the Tourist Information office and they did not know. I am intrigued....

Caroline Morgan

Lower Withington   


In your last edition you asked if readers could give any information about the meaning of a mark in a wall.

The mark is a ‘cut bench mark’ placed by the Ordnance Survey. The horizontal line is a known height above sea level. The locations of these marks are shown on the old 6ins scale OS maps. They are often located close to church spires which were used for triangulation.

More information can be found at John Swash Via email The sign shown in the letter from Caroline Morgan is an Ordnance Survey Bench Mark which denotes the height above the Ordnance Datum level which is set as the sea level at Newlyn.

These marks are situated throughout the British Isles and allow the height of one spot to be compared with another and has numerous uses in the construction industry.

Stewart Bailey

Via email



Caroline Morgan may be interested to learn that the sign she photographed is a benchmark – that is a surveyor’s mark cut in a wall, pillar or building.

During the late 19th century the Ordnance Survey, then a government department, undertook an accurate survey to map the whole of the UK.

As part of this survey, heights above sea level were recorded throughout the country.

These were inscribed on long-standing buildings such as churches for future survey work that included levelling. Details of the location of their positions and heights above sea level are recorded on OS large scale maps.

David Brown




The term benchmark, or bench mark, originates from the chiselled horizontal marks that surveyors made in stone structures, into which an angle-iron could be placed to form a ‘bench’ for a levelling rod, thus ensuring that a levelling rod could be accurately repositioned in the same place in the future. These marks were usually indicated with a chiselled arrow below the horizontal line.

Ian Jones