.. the Borderers had signals, and places of rendezvous, peculiar to each tribe. If the party set forward before all the members had joined, a mark, cut in the turf, or on the bark of a tree, pointed out to the stragglers the direction which the main body had pursued.*
*At Linton, in Roxburghshire, there is a circle of stones surrounding a smooth plot of turf, called the Tryst, or place of appointment, which tradition avers to have been the rendezvous of the neighbouring warriors. The name of the leader was cut in the turf, and the arrangement of the letters announced to his followers the course which he had taken. See Statistical Account of the Parish of Linton.
p lxxxix in the 1821 (5th) edition of 'Minstrelsy of the Scottish Border' by Walter Scott - on Google Books.
In different parishes, such as Moorbattle, Linton, and others, are to be found what are called tryst stanes. These are great stones commonly situated on high grounds. They are placed perpendicularly in rows, not unfrequently in a circular direction. It is said, as also the name imports, that in times of hostility they marked the places of resort for the borderers when they were assembling for any expedition of importance.
'The beauties of Scotland' (1805) by Robert Forsyth, p103 - also on Google Books.