Washers serve two primary purposes: they distribute the load of the tightened fastener over a larger surface area to prevent damage to your material, and they help prevent the nut or bolt from loosening due to vibration. A standard flat washer spreads the load, while a spring washer (or split-lock washer) adds tension to resist vibration and movement.

Those numbers (such as 8.8, 10.9, or 12.9) indicate the bolt's tensile strength and yield strength grade. For example, an 8.8 grade bolt is a high-tensile structural bolt commonly used in general engineering, while 10.9 and 12.9 grades offer even higher strength for demanding heavy machinery and automotive applications.

Stainless steel fasteners are highly prone to a phenomenon called "thread galling" or cold-welding, where friction causes the threads to lock up and seize during tightening. To prevent this, always ensure the threads are free of debris, tighten the nut slowly to reduce heat buildup, and apply an anti-seize compound or specialist lubricant before assembly.