A professional who tends machine that coats strands of yarn with size to stiffen and strengthen yarn for further processing. Respnsibilities include:

• Positions yarn bobbins and takeup cylinders on spindles of machine.
• Threads yarn over fingers of tension guides, across size-covered rollers, and around cylinders.
• Determines tension of yarn strands, using tensiometer.
• Pulls or releases yarn between tension guide and takeup cylinder to increase or decrease tension.
• Turns valve to admit size into retaining trough of machine.
• Observes machine to detect deviation of flow or supply of size from standard and notifies knitting-machine fixer, head of malfunction.
• Observes machine to detect yarn breakage and ties knot or rewraps yarn end around sizing cylinder to repair breaks.
• Doffs and labels cylinders of sized yarn.
• May mix size, following formula.