Related Clues:

• Doc. with a ltr.
• Letters on a can of motor oil
• Cover-letter letters
• Something inside an envelope: Abbr.
• Motor oil letters
• Compton's, for one: Abbr.
• SASE, often
• R.S.V.P. facilitator: Abbr.
• Robbie's grace continues
• Reply facilitator: Abbr.
• Letter-bottom abbr.
• Convenient encl.
• Util. bill encl.
• An SASE is one
• Env. in an env., say