It was not an easy task. If we laid all the tape - and there were nine miles of it - on the night before the attack, any German patrol stumbling on it would know what we were up to. If we waited until the night of the attack before laying it and then spent too much time over the job, the assaulting troops would be caught by daylight before they had dug in on their objectives. However by planning and much practice, a solution had been found. We and the rest of the Division had already fought the battle three times in "M" Training Area behind our lines, and after a good deal of trial and error a drill had been evolved.
We began work on the night of 19/20 October. The first difficulty was to pinpoint the ends of the start-line. If they were wrongly placed the whole layout would be wrong; and the only way to fix them in surroundings as featureless as the ocean was to have several officers start with compasses in their hands from known points and pace carefully along on bearings until they converged. Once these key points had been fixed, a drum of signal cable, invisible in the dark, was unrolled along the start-line and tied to short metal pickets which we hammered in every fifty yards. It was unlikely that the Boche would find the cable, and if they did it would not tell them much.
Sixty men finished this part of the job in one night. On the night of October 21/22 we were out again; and by dawn the nine routes had been plotted, the nine cables laid, and the pickets driven in. We still had a night in hand before the attack; and Colonel Stirling, who had practically lived in No Man's land since the taping began, spent it guiding representatives of the other battalions along the cable to show them the layout and allow them to mark their own boundaries and centre-points. It was found by pacing that the routes delivered units on to the start-line very accurately throughout its length.
The spade-work was now complete. On the night of the battle, parties went out at dusk with drums of white tape, unrolled them, fixed the tape to the cable at intervals so that it could not be blown or dragged away; and ninety minutes later nine miles of start-line and routes were clearly marked.
Borthwick, Battalion (London, 1994) pp.30-31