These flags are placed on the top of the Z axis lead screws on a Prusa type printer. The flags are a quick calibration indicator. When your stepper motors are not powered, they can easily be moved and the calibration of your printer will be off.

After calibrating and leveling the bed, align both flags to point in the same direction. When you start a printing session, you can quickly check the calibration flags.

Print 2 caps and 2 flags. The flags are glued into the slot in the caps.