Close the letter affirmatively. Reiterate your recommendation of the candidate and, if appropriate, invite the recipient to contact you. For example, say, "For all of these reasons, I think Michael will make a fine addition to your team. Should you have any questions, I invite you to contact me at the number or address, above
Some applications, such as professional schools give applicants the choice to waive their right to view their letters or not. Usually, applicants are encouraged to waive their rights because if they do not, it is a sign they are not confident in their recommenders.