Final answer:
A high grade number for a fastener indicates a stronger fastener that can withstand greater forces. This is crucial for the safety and longevity of structures or machines where these fasteners are used.
Step-by-step explanation:
When talking about a fastener, such as a bolt, a high grade number generally refers to the strength of the fastener. Fastener grades denote the material properties, including tensile strength, yield strength, and hardness. The higher the grade, the stronger the fastener - meaning it can withstand more force or load without failing.
The grading system for bolts is standardized, with common grades for carbon steel bolts including Grade 2, Grade 5, and Grade 8 in the United States, with Grade 8 being the strongest of these. For metric bolts, the property classes such as 8.8, 10.9, or 12.9 serve a similar purpose with a class 12.9 bolt being one of the highest and therefore strongest commercially available.
Therefore, a high grade number signifies a fastener that can be used in applications where high tensile strength is required, which is essential for ensuring the safety and durability of structures or machinery.