Non-OS marks
From TrigpointingUK
A Facebook page is available for discussing the larger-sized non-OS stations. There is a site for logging EABM markers.
Numerous other bolts, rivets and miscellaneous markers exist. These are often found in pavements, bridges and along river banks. Their purpose is sometimes obscure and uninteresting. Here are a few examples:
rivet on a step approx locn SE 2807 3702
National Rivers Authority block
