Set up during the initial setting out of work and before excavation of foundations. Two adjacent profiles, set square, are arranged for each external corner and positioned well clear of trench lines; each wooden profile is made up of a horizontal rail held by two stout pegs. The rail is used to mark out the face of wall and the trench lines. A ranging line is secured from corner to corner from which the trench lines are set and following excavation the work, below ground level, is set out by plumbing down from the line.