I was first introduced to butterfly key joinery in college by a visiting artist who had served as apprentice to the millwright for the United Kingdom's Society for the Protection of Ancient Buildings. He used the technique in part as a repair and visual design element on pieces of wood with defects that he found aesthetically interesting. In his honor, I'll be using butterfly keys to mend the piece of 5/4 jatoba pictured here - which, as you can see, offers plenty of opportunity for me to hone my skills.
There are probably many ways to "correctly" install butterfly keys, so if you're new to the technique and want to give it a try, check around to find the method that suits you best. The first few steps of the one I'll be using will be to cut the key with an Ikedame dovetail saw, trace the key's shape onto the piece of jatoba, and then route the basic shape of the mortise "freehand" with a plunge router. After that, I'll trim the edges of the mortise, glue in the key and trim it flush with the surface of the Jatoba. In Butterfly Key Joinery - Part II (next Wednesday or so) I'll mark and cut the keys, and pass on my method (and any others that I hear about in the mean time) for making sure that the keys fit into the mortises correctly.
*Tom Noone's table was featured in the March/April 1992 issue of the Woodworker's Journal. A complete set of plans are available at the Woodworker's Journal website.
Original article and pictures take http://www.rockler.com/how-to/butterfly-key-joinery-part-i site