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A Feno Marker is a type of survey marker, developed by the French company Faynot, which is quick to install and well anchored [1]. 15 instances occur in the OSGB36 list [2]. A listing is available from T:UK

T:UK Station name Order Computed Block
TP7808 Cattlelaith Lane 13 1987 SE44
TP7808 Cattlelaith Lane 13 1989 SE44
TP7807 Kings Standard Hill (1987) 13 1987 SE44
TP7793 Spitalgap Lane 13 1987 SE44
TP7793 Spitalgap Lane 13 1989 SE44
TP7451 Gibbet Hill 3 1989 SK73
TP7792 Woodlands 3 1987 SE44
TP7839 New Champany Reservoir 13 1988 SE22
TP7791 Round Green 13 1988 SK39
TP7794 Rother Valley 13 1988 SK58
TP7790 Lizard Lane 13 1989 NZ29
TP7795 Hammersley Lane 30 1988 TQ08
TP7788 Berwick Golf Course 3 1987 NT86
TP7450 Toton Sidings 3 1988 SK73
TP7789 Westlea 13 1989 NZ42

The installation of a Fenomark has been described as follows: "Apart from the obvious yellow, white or whatever colour block at the top, the mark itself is a hollow rod of variable length. Within the rod are three strands of galvanised rod about 5mms in diameter. After the rod is driven onto the ground a tool is driven down the centre of the tube which drives the 3 rods out the bottom. These are designed to twist and provide a corkscrew anchor into the soil. Consequently ... very difficult to extract. The system was originally developed in France for anchors for grape vine wires." [3]

Fenomarks in the UK are not exclusive to the OS. For example, they can be found along the S bank of the Humber estuary, E of the bridge, where they may have been placed by the National Rivers Authority (NRA). Elsewhere, non-OS Fenomarks have been used in road construction.


  1. http://www.mapc.com.au/feno_marks_72.html
  2. https://www.ordnancesurvey.co.uk/legacy/docs/gps/CompleteTrigArchive.zip
  3. emails from Ian Wilson and Graham Pennington to the Trigonomy list, 14/02/2013