• Door with safe lock, no more thefts. (When locked, you can't open it with levers or buttons outside)
  
• Safe item input.
  
• See what items are offered to you in a glass wall.
  
• Other person can't see what are you doing at the other side.
  
• Stop the trade whenever you want, and the items will go back with their owners.
  
• When both players agree with the trade, it starts.
  
• Fully hidden redstone device.
  

Additional Notes