Related Clues:

• Is that the way to make the sentry stout round the river?
• Would Sen try to get the mail before it goes?
• Perhaps the collecting of mail is not an indoor job
• No delivery of mail here - it seems too isolated
• Mail on sentry go?
• Collection of mail for the sentry?
• How letters leave the sentry
• One must keep a watch on the letters from the army
• Collection of letters from sentries?
• Not at head office for 1 across
• Sentry go there as letters go?
• How the letters get sent from the sentries
• He's a watch on the leter being sent, it seems
• That's the letter the sentry is sending
• One keeps a watch on the mail one sends