Sherlock describes Devon Gaspar's message to Moriarity as written using a technique called the Ave Maria Cipher (a type of steganography). The Ave Maria Cipher uses a word, from a predetermined list, to represent a letter. The letters are replaced by the corresponding word in the message so only certain words have any significance. Only the recipient knows the hidden information is there. Devon's message is 75 letters long (not counting spaces and punctuation) so the ad in the newspaper for a used car would need to contain 75 seemingly random words, in addition to those actually about the used car.