On 2011-09-06 00:00:20 -0400, Father Haskell said:

Except Fender has been harassing small-time builders
of cigar box guitars, since cigar box guitars are
square, and Fender, which owns Gretsch, who built
Bo Diddley's signature instruments, owns the patent on
square guitars.

Technically, Bo's guitars were rectangular. According to some sources
he built the first one, so "prior use" should invalidate any Gretsch
patent claim, as would the famous "log" built by Les Paul. Leo Fender
also seems to have built a "square" prototype.