Finishing touches and added details are generally what set any great design apart from one that is nice but ordinary. For example, a room filled with beautiful furniture tends to look unfinished until the accessories have been added. A brand new shiny car is cheapened if it is missing hubcaps. The same is true with custom frame design. Adding the right details can take framing from ordinary to extraordinary.
Fillets are one of the options, you can use to add finishing touches to the frame design. Fortunately there are hundreds of fillet options to chose from today. That wasn’t the case in the past, There isn’t good data to show when fillets were first introduced to custom framing.
Fillets never seemed to gain mainstream popularity until recently. In the past 20 years they finally became a sensation. Today, there are fillet choices in a wide range of colors, styles and profile shapes. There are great options for nearly any framing project. Today it is most common to see fillets in mat openings, but they are still used inside frames, too. They can also be used in a few other, less common ways.
PFM, May 2010: Article by Greg Perkins. Page 26