The first person to open the Trade-O-Mat's GUI becomes its owner. The owner should put the item he/she would like and its quantity in the top left slot of the GUI. Next, the owner should place the item sold and its quantity in the bottom left slot. The quantities are very important. The right two slots are spaces to normally do trade, even as owner. It is recommended to put a sign or some other form of notification of what the prices are, as the Trade-O-Mat does not display these prices. Note: Armor/Tool/Weapon Durabilities DO matter, as the Trade-O-Mat trades by Item ID.
The Trade-O-Mat will draw items from an adjacent chest for purchase, and put payment in the same chest. It is recommended to use a Personal Safe , as it provides a barrier, so customers cannot steal your items. Up to 6 Trade-O-Mats can surround 1 Chest, or 10 for a double-Chest, though one slot should be left for accessing payment and refilling sales.
All non-ops and non-owners, when opening the GUI, will only see two slots. The buyer should insert the payment in the top slot, and will receive the item in the bottom slot. Should a customer put twice as much payment than needed, he will receive double the regular amount. (i.e. A trade occurs, with the customer needing to pay 8 Cobblestone to gain 1 Wood Plank. If the customer inserts 16 Cobblestone instead, the customer will receive 2 Wood Planks.)
Should a player accidentally forget to access a Trade-O-Mat, and not become an owner, then they should notify a Server Op, as they can also access and remove Trade-O-Mats.