Fairing a surface removes the highs and lows so the surface is level. It can mean filling holes and low areas, reshaping voids, or grinding down bumps so they blend in with the surrounding surface, appearing level, or "fair" to the eye, to the touch, or to the fairing batten.

The material for filling or shaping is called a fairing compound or fairing putty, which contains some type of resin—either epoxy, polyester, or vinyl ester. For convenience, there are premixed fairing putties, or you can make your own.

There are a lot of reasons to fair a surface while building or repairing a boat. Examples include:

• Making the entire hull surface fair during construction, especially for wooden boats
• Fairing large areas of a hull surface misshapen due to, for example, bowing out at the bulkheads as a result of years of hull stresses
• Fairing small gouges and dents on wood, fiberglass, aluminum, or steel hulls before applying primer and painting
• Fairing gelcoat imperfections above the waterline
• Filling in holes after grinding down gelcoat blisters below the waterline before finishing with an epoxy barrier coat and antifouling bottom paint
• Fairing a hull surface prior to wet layup with fiberglass to ensure an even surface because fiberglass is difficult to sand
• Fairing a small area of fiberglass cloth that didn’t quite get filled in by the epoxy overcoats after wet layup and before priming and finishing
• Reshaping and fairing damaged underwater appendages such as the rudder and keel for added speed
• Filling holes after removing hardware
• Fairing an entire hull before a paint job