A glazier is a person who fixes broken windows, often using traditional methods. Today, the term is a bit outdated as windows are modular and are replaced by taking out an old unit and installing another. This does not mean that hiring a glazier is obsolete. A person who is expert at cutting and installing straight pieces of glass can be valuable, especially when repairing traditional window panes.
This is not a job that can be done by an amateur. A modular window might able to be replaced by an amateur if the law allows it, but the skills needed to cut and install individual pieces of glass is a skilled trade that requires certification. At stake are the safety of the worker as well as the integrity of the building. Commercial buildings and residences are expected to have airtight and secure windows, and a professional is needed to do the job.
A glazier can repair a broken window without trouble. Large front windows, especially for residences, are often divided into smaller sections using a grid window pane. If one window is broken, the rest of the glass structure is usually unaffected. A small piece can be easily replaced. The worker makes measurements of the damaged glass, cuts a replacement, and then removes the old glass and its fitting however is most practical.
Even whenever a window fitting has to be cut instead of disassembled, the resulting repair should be precise and practically as good as new. If the job is sloppy and stands out, then consider hiring a better glazier who knows how to do the job right. A broken window is also a hazard, and all the pieces should be found and disposed of in a safe container.
A window replacement specialist has other uses. Some windows are compound and use small sections of cut glass to form a mosaic display. This is common in churches, but many buildings also use the technique. A glazier should be familiar with replacing individual sections, even if it means melting tin or lead binding and then gluing a fresh piece in place.
Glaziers commonly work on storefronts, which generally require a large piece of glass to be cut to specific dimensions and then installed to the storefront. A professional either has large cutting equipment in a shop or is able to cut glass with power tools. Even using improvised methods, the end result should be gorgeous and represent the business well. Glaziers may or may not paint letters on the window, as this is another profession.