MUTOH ValueJet VJ-1638UR Operation Manual page 30

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30 Loading Roll Media onto the Roll media holder
Attach Roll media holder (right) to the roll media and tighten Fixing
lever.
Loosen the Fixing levers of the right and left Roll media holders, move
the roll media to the center.
Press Roll media holder toward the printer and fix the Fixing levers.
Note
When tightening Fixing lever, press Roll media holder toward the printer.
If you do not press Roll media holder, Fixing lever may not be completely locked
because of the weight of the roll media.