Cut marks form the vast majority bench marks used by the Ordnance Survey from around the 1840s up until the last ones cut in the 1980s
The latest BMs were cut in and around the new town of Milton Keynes which also added a “stud” type bench mark to the set!
Other types of BMs were added to the initial survey (1840-1860) BMs of “Cut Marks” and “Cut Marks with Bolts”
at some stage the “Rivet” type BM was added to the set to be used on horizontal surfaces such as steps or parapets.
The second geodetic levelling survey (1912-21 2GL) introduced the various classes of levels with the first class, which later became the primary, was the highest, most accurate, levels to be used and are the only part of the 2GL network that the OS still use.
For the second class levels OS introduced the “Flush Bracket” which were especially manufactured and positioned to provide the best possible secondary levelling accuracy required by using an adjustable bracket that attached to the FB to provide the “Level bench” for resting the levelling staff on.
The third class or tertiary levelling relied mainly on the “Cut marks” but also used Rivets, Bolts, Pivots and Projecting Brackets.