Back A columnar transposition does a row-column transpose (see below).
Columnar Transposition Cipher
The following is taken from http://practicalcryptography.com/ciphers/columnar-transposition-cipher/. First we use a key, such as "GERMAN", and where the number of columns will be equal to the key length (in this case we have six columns). Let's start with a message of:
We then write the message with the key word in the first row:
G E R M A N d e f e n d t h e e a s t w a l l o f t h e c a s t l e
and then arrange alphabetically for the key word:
A E G M N R n e d e d f a h t e s e l w t l o a c t f e a h t s e l
and then read the cipher from the columns down: