With reference to John Constable's letter (Chain mail, NCE Letters 19 August). I think the chainman is still widely used but few younger people realise where the term comes from or have even seen a chain, never mind used one. I certainly have.
With respect to errors, in 1971 I used a 100m steel band to set out a pumping station at Colliers Wood on the original London Ring Main. The main shaft was in the centre of two 30ft diameter underground pumping chambers. I set the shaft out in two directions but could not get the centre to agree by exactly 1m.
The error was in the band. I had one measurement of over 65m to get between some houses. The stamping on the band had slipped at 61m and had then gone to 63m. It had then reverted back at 91m. So the band was a 100m long but it had an error in the middle.
Luckily for me I had a wise old site agent who said I should check the full length of the band.
As for the band maker, it just said 'how unusual' and sent us another one. I wonder if John checked his chain?
Jack Knight, jknight@haswell. com