Our proofreading course students often ask about the BSI proofreading symbols A3 and B6.
This isn’t surprising. Anyone under 50 would find them strange.
A3 is virtually redundant now. It refers to ye olde days when typesetting was done by printers using a linotype machine. The type was set in strips of lead, or ‘hot metal’.
The lines were separated by another strip of lead, but sometimes this wasn’t pushed down properly – so it literally had to be pressed down, otherwise that part of the document would appear blurred. Sometimes printers used a hammer to flatten it properly!
B6 is related. Sometimes, the above-mentioned printer might use his hammer a bit too enthusiastically, and damage some of the lead characters. So this instruction is to replace the damaged ones.
Believe me, this wasn’t the only occasion a hammer was used in the printing works! Especially after said printer had been down the pub during his lunch break.
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