From speedbump59
It will cut the patch to the same size and shape and drop it into the space as a plug. The tiny gap around the patch will be filled with paintable sealant that will stretch and compress as the fuselage is pressurized and unpressurized.
Then mechanics will work on the inside, gluing a splice plate to the original skin and to the patch, overlapping both by about 4 inches.
Interesting... this is a somewhat unexpected approach. Sounds like a mix between metal repair and wood repair. My spontaneous(sp?) reaction is that I would want to invert the plug method (that is, inserting it from the inside), but if it works, it works. Would love to see a paper on this!