What type of writing instrument is not permissible for the back of the sticker?

The choice of writing instrument that is not permissible for the back of the inspection sticker is typically one that could potentially damage or compromise the integrity of the sticker. A pen Sharpie, which uses a permanent ink that may bleed or spread if exposed to moisture or varying temperatures, can interfere with the sticker's readability and durability. This can lead to issues during inspections or in the event that the sticker needs to be verified or checked, as a well-maintained and legible sticker is crucial for compliance and identification purposes.

In contrast, other instruments like permanent ink markers, fountain pens, and gel pens may be preferable because they can offer more controlled application and are less likely to bleed through. These types of pens can allow for clear and precise markings without the same risks associated with the ink from a pen Sharpie, which might cause smudging or degradation of the sticker's material. Knowing the specifications for what is allowed helps ensure that the inspection process remains efficient and that all documentation remains in good condition.