Final answer:
Pencil should never be used to mark and identify instruments because its markings are not permanent and can introduce contaminants, compromising sterility.
Step-by-step explanation:
When marking and identifying instruments, a pencil should NEVER be used. The use of pencil is not suitable for several reasons. First, the markings made by a pencil can easily be erased, rubbed off, or smudged, leading to potential misidentification of instruments.
Furthermore, pencils are not sterile and can introduce contaminants onto the surface of medical instruments, which can be a significant issue in environments that require strict sterility, such as operating rooms or laboratories. Instead, marking methods such as engraving, etching, or the use of permanent marking techniques that can withstand high temperatures and sterilization processes are generally preferred.