When a window is National Certified Testing Labs (NCTL)-validated, it meets certain standards and is at a proper quality control level.

When a window, door, or skylight has an NFRC rating it means that an energy rating was appropriated by National Fenestration Rating Council (NFRC), a non-profit group of manufacturers, builders, designers, government officials, utilities, and consumers providing unbiased energy performance ratings.

A nailing fin, or brick mold, is a strip of metal secured to the main frame of a window and used to strengthen and secure a unit to an opening.