Covered Bolts

Covered bolt at Redscar

Exposed detector plate at Wansfell Pike

Covered bolt at Fochno

Covered bolt at Therfield Heath

Lake District

A very small number of bolts have been found covered with a metal plate approx 12" square with the warning sign 'ORDNANCE / SURVEY / DO NOT / DISTURB' embossed on a raised circular disc at the centre of the plate. To date (September 2024) all of these have been located within the Lake District National Park.

'Covered Bolt' is a trig baggers term; the corresponding OS term for the cover is 'Detector Plate'. This is mentioned, for example, in the Office File sketches for Ponsonby Fell and Kentmere Hall. In T:UK and OSGB36 the trig mark itself is listed as either a Bolt or Buried Block. As with Concrete Rings, the purpose of the cover is to aid in the detection of the trig when using a metal detector.

Trig Stations with a Covered Bolt

T:UK	Station name	Order	Computed	Block	Date found	Finder
TP16495	Blake Fell	3	1952	NY11	5 Nov 2023	CJO
TP16484	Clints	3	1952	NY11	6 Aug 2023	CJO
TP17120	Gilpin Park	3	1950	SD47	26 Feb 2022	peregrinus
TP17121	Kentmere Hall	3	1950	SD47	11 Feb 2023	peregrinus
TP16490	Lorton	3	1952	NY11	13 Aug 2023	CJO
TP8079	Lowick	2	1950	SD47	14 Sep 2013	peregrinus
TP16492	Ponsonby Fell	2	1952	NY11	16 Oct 2019	Dusty
TP8081	Redscar	3	1950	SD47	18 Apr 2014	painterman61
TP13003	Top o' Selside	2	1950	SD47	10 Oct 2019	Dusty
TP7820	Wansfell Pike	2	1950	SD47	22 Apr 2020	projectionist
TP16497	Watch Hill	3	1952	NY11	6 Aug 2023	CJO

Trig Stations where a Covered Bolt is suspected but not confirmed

T:UK	Station name	Order	Computed	Block	Notes

Others

A single instance of a cover with a different style has been found at Fochno in Dyfed. This in turn resembles the passive station sketch for Pegler's Tump. An unmarked iron plate covers the bolt at Therfield Heath.