A full block style format for a letter means all the text is left justified. This varies from a semi-modified block style format in which some elements are right justified. Full block format is a formal style that is common for business letters.
Two spaces, or line breaks, separate the date from the inside address, although it's common to see four line breaks. Two spaces also separate the address from the salutation, the salutation from the body and the body from the closing. Four spaces separate the closing words, such as "Sincerely yours," from the writer's printed name. This allows space for the signature.