| M | S | I | B | R | O | R | S | E | E | V | U | E | E | M | C | O | R | E | R | E | L | I | D |
| E | T | O | E | P | Q | E | N | R | E | R | N | S | E | R | Y | E | C | O | L | L | E | R | E |
| U | S | P | L | U | R | C | E | L | O | A | J | A | E | H | U | H | P | F | A | S | O | N | N |
| O | A | A | E | P | I | U | A | P | P | E | A | C | U | Q | A | R | U | O | P | O | E | I | I |
| R | R | M | I | A | F | D | A | A | R | Q | U | B | O | Z | A | E | G | E | R | S | F | S | X |
Here an inspection shows this to be Case [1-f], alternate diagonal, and the text to be “ME SITUO SOBRE PARRAL PORQUE ME PRESENCIA FUE REVELADA POR U”; here the sense breaks but note that U is the twelfth letter of the line and continue as if the rectangle were 5 × 12 and we have “NA PAREJA QU.” Now inspect the second rectangle of 5 × 12 in the same way and the sense continues “E SE ME ACERCO Y HUBO QUE RECHAZAR POR EL FUEGO ALLI ESRERO ORDENES FINISX”.
The practical way of examining a cipher of this type is to have several men prepare rectangles of different dimensions, using the letters of the cipher in the order received. The rectangles can be inspected very rapidly when once prepared. Note that the dimensions of any rectangle will rarely be such as to contain more than fifty letters, on account of the necessity of filling up a rectangle with nulls if the number of letters of the message is just a little greater than a multiple of the rectangle. Also large rectangles give, for all but the diagonal method, whole words in a line or column and these are easily noted.
The following ciphers come under Case 1:
Case 1-i.—The rail fence cipher, useful as an operators’ cipher but permits of no variation and is therefore read almost as easily as straight text when the method is known. The message:
HOSTILE CAVALRY HAS RETIRED
is written:
| O T L C V L Y A R T R D |
| H S I E A A R H S E I E |
and is sent: