Ron Lake, who came up with the notion of the interframe, created it as a way to protect the scale material from damage from all sides. It's useful for protecting delicate, thin material -- like fine black lip pearl, antique tortoise shell, green sea snail shell, semiprecious stone, and such. It allows a knifemaker to use much smaller and thinner pieces of scale material than they could otherwise use -- since the size of scale material required is only whatever size pockets the knifemaker wants to use (and can even use multiple pockets if desired) -- and allows them to use some exquisite pieces of material that are just too small to use any other way. Some makers even create elaborate mosaics from many pieces of pearl within an interframe pocket - which would be far too delicate to be used as a normal scale material.
I should note that some antique knives look just like a modern interframe -- the only difference is that in all the old ones I've seen, the scale material will be something that can be cast or formed into the pocket, not machined and inset (and the pocket was originally stamped or forged into the handle material, not machined).
I guess you learn something everyday. :thumbup:
