Pen
Else clues• Box in
• Cocoon
• Completely surround
• Corral
• Fence in
• Fence off
• Frame
• Hem in
• Include in the envelope
• Include, in a way
• Place in an envelope
• Put a fence around
• Put in the envelope
• Put in, as with a letter
• Ring
• Stuff envelopes
• Stuff into an envelope
• Surround
• Surround completely
• Wall in
• Wall off