A professional who tends machine that forms opening (valve) in paper bags through which loose materials, such as cement, sugar, lime, fertilizers, and sand are poured into bag. Responsibilities include:

• Positions unsewed paper bag on machine bed between guide arms.
• Depresses pedal or moves lever to start machine that automatically creases and folds bottom of paper bag to form valve, and discharges it onto conveyor.
• May tend sleeve machine that automatically cuts and glues strips of paper (sleeves) used to close valves of filled bags.
• May tend machine that forms valve and sews ends of bags and be designated combination valving-and-sewing-machine operator.