When you were deemed proficient in your craft one of the more awkward jobs was to make corrections on press. Qualitex printed a book for the Guild of Graduates, so this involved climbing into the bowels of one of the larger Heidelberg flatbed cylinder presses (I seem to remember Qualitex having 5 flatbeds in total, 3 small and 2 large). The job itself was a small book, about A6, with 32 pages at a time imposed on the bed. If, for some reason, the type took a bash or was just badly worn, then you had to replace the bad characters in the chase. Invariably, the type that needed replacing was in the back of the press and in the dark. So you had to print the text onto your hand and try to work out what was what.
These flatbeds were generally regarded as being on the cutting edge of letterpress printing and, even in the mid-seventies were producing quality print. However, it wasn't long before developments in litho printing overtook these big cumbersome beasts and reduced them to cutting and creasing work, which they still do today.