When it gets below 74, they won't knit properly, over 78 and they won't knit properly. You may have 5 or 6 good stockings out of 30. You will have to throw out the rest. These studs tell the machine what it should do, so every design needs a new stud pattern, which is a huge operation. After manufacture each stocking is seamed, one at a time.
People often ask why there is a hole at the top of the seam.
Every stocking is manufactured white and must be colour dyed. They must then be 'Boarded' where each stocking is pulled over a flat wooden leg and steamed. This tightens the knit, defines the leg shape correctly and removes creases. Thereafter each stocking is checked for size to ensure that pairs match. Quality control for faults large and small can mean a third of production can be lost.