Mobile printers like the Zebra QLn420 support roll labels with black timing marks. 

However, they can also use regular labels with a gap sensor (no black mark), which end up being cheaper to buy.

If you’re switching to gap sensor labels, you’ll need to adjust the settings on your printer.

Below are the instructions on how to switch from timing mark to gap sensor on a Zebra QLn420:

  1. Turn on the printer
  2. Press Home and then Settings
  3. Use the right arrow button to navigate to Media Type
  4. Press the down arrow to enter the default password, which can be found in the manual
  5. Press Done
  6. Press the down arrow to select media type
  7. Press Home