TheCodeBreakers
Like the K2, it used a
keynumber, but it differed in being copied off vertically instead of
horizontally, and in having a pattern of holes in the transposition blocks.
These holes were left blank when the code groups are inscribed into the
block. For example, letting the alphabet from A to Y serve as the code
message:
[CodeBreakers 020.jpg]
The letters were transcribed in columns in the order of the
keynumbers, skipping over the blanks: BJMV EHKT NW CGORX AFILQU DPSY.
This would be sent in the usual five-letter groups.
The first step in solving a columnar transposition like this, but
without blanks, is to cut the cryptogram into the approximately equal
segments that the cryptanalyst believes represent the columns of the
original block. The blanks vastly increase the difficulty of this essential
first step because they vary the length of the column segments. The
second step is to reconstruct the block by trying one segment next to the
annaabi.ee 
