Using line bars
Les Maxwell
Line bars can be a bit fiddly to set up but adding an additional winged nut (coach bolts are best) in the centre of the clamp makes life a bit easier.
Firstly set bars in the ground as normal for the base width, allowing for a bit of flexibility in movement
Then attach the clamp to the bars and set the correct height of the clamp (wall height below copes) making sure its level
Tighten the middle nut and also one of the end nuts but leave a bit of give on the remaining nut so you can move the bar along the clamp. It is a good idea to mark the centre of the clamp
Set bar to the correct distance from the middle mark (half the width of the wall below copes) then hammer the rod home and tighten the nut
Loosen the nut on the opposite side and repeat the process
A valuable piece of kit is a Stanley line spirit level that attaches to string lines and is useful when setting your lines level. At about £3, no waller shouldn't be without one