first class(noun) the highest rank in a classification. first class, 1st class, first-class mail, 1st-class mail(noun) mail that includes letters and postcards and packages sealed against inspection. first class(adj) the most expensive accommodations on a ship or train or plane.
A very basic sliding glass door, without professional installation, can cost $300 to $500, and this is the type of door most people think of when they hear the term sliding glass door â a six-foot pair of plain glass panels inside a simple frame. An eight-foot door can run $800 to $1,200 without professional installation.
1 Exterior door replacement in an existing space costs around $250. To create a new space for sliding glass or French doors it might cost $500 to $1,500. 2  A basic knob and lock set costs $50 to $100; designer exterior door hardware costs more.  Exterior door installation is a manageable DIY project.