A glazier is a tradesperson responsible for cutting, installing, and removing glass (and materials used as substitutes for glass, such as some plastics). They also refer to blueprints to figure out the size, shape, and location of the glass in the building. They may have to consider the type and size of scaffolding they need to stand on to fit and install the glass. Glaziers may work with glass in various surfaces and settings, such as cutting and installing windows, doors, shower doors, skylights, storefronts, display cases, mirrors, facades, interior walls, ceilings, and tabletops.

The Occupational Outlook Handbook of the U.S. Department of Labor lists the following as typical tasks for a glazier:

The National Occupational Analysis recognized by the Canadian Council of Directors of Apprenticeship separates the trade into 5 blocks of skills, each with a list of skills, and a list of tasks and subtasks a journeyman is expected to be able to accomplish:

Tools used by glaziers "include cutting boards, glass-cutting blades, straightedges, glazing knives, saws, drills, grinders, putty,scrapers, sandpaper, sanding blocks, 5 in 1's respirator/dust mask and glazing compounds."

Some glaziers work specifically with glass in motor vehicles; other work specifically with the safety glass used in aircraft. Others repair old antique windows and doors that need glass replaced.

Glaziers are typically educated at the high school diploma or equivalent level and learn the skills of the trade through an apprenticeship program, which in the U.S. is typically four years.

In the U.S., apprenticeship programs are offered through the National Glass Association as well as trade associations and local contractors' associations. A large portion of glaziers in the United States are members of the IUPAT, the International Union of Painters and Allied Trades which offers its own apprenticeship program which consists of 8000 hours of on the job training and 4 years of classroom education. Because of this, IUPAT Glaziers tend to be well rounded in all aspects of the trade, and therefore carry a higher production rate, face fewer health & safety risks and command a higher pay rate.

In Canada, glaziers usually go through a formal apprenticeship which includes about four years of on-the-job experience combined with classroom study in order to get certified. Unions and many employers offer these apprenticeships. To become an apprentice, one must be at least 18 years old and have a graduated high school. Once a person is certified, they will be eligible to apply for the Red Seal allowing the person to work anywhere in Canada without re-certifying. In Ontario, Canada, apprenticeships are offered at the provincial level and certified through the Ontario College of Trades.