Mirrors suspended above design tables used to be the best way to help customers visualize what their finished framing would look like.
Nowadays we have a better way: snap a digital photo using a ceiling-mounted camera and use a visualization program to show customers how the finished framing would look.
Aside from helping indecisive customers decide, a viz system is useful for making digital composite images for advertising and to show customers. For instance, we've earned some commercial jobs simply because we included digital images of the finished framing with our proposals.