Related Clues:

• QE2, for one
• Mail in a box
• Challenge for a shortstop
• It may go in a lock
• Ocean liner, for one
• Mail out
• A hard hit single, maybe
• Hard-hit ball
• Send in a crate
• Eye enhancer
• Mail away
• Word with hard or head
• Kind of notes
• Scow or skiff
• Salt container?