VMS Help MERGE, Specification File Qualifiers, /PAD, Qualifier Value  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 single-character

    Specifies the character that the Sort utiltiy will use to pad a
    string. Characters, decimal, octal, or hexadecimal digits can be
    used. The pad character should be specified as follows:

    o  Use quotation marks for a character. For example, " # " would
       specify the number sign.

    o  Use decimal radix for decimal digits. For example, %D35 would
       specify the decimal number 35.

    o  Use octal radix for octal digits. For example, %O043 would
       specify the octal number 043.

    o  Use hexadecimal radix for hexadecimal digits. For example,
       %X23 would specify the hexadecimal number 23.