EDIT - Solved, thanks to everyone who replied!Right, so I'm currently setting up a mall and making a section that sells enchanted books. I understand that I need to make [SLOT] signs to sell the book but I'm still a little confused around them, even after reading the wiki.From what I understand, say I want to sell an unbreaking III enchanted book with a [SLOT 1] sign, I would put an unbreaking III book in slot one of the chest and fill the rest of the chest with unbreaking III enchanted books too. The book in slot one of the chest would be used as a reference to tell the sign that this item is the only thing that should be sold from this chest because it is in slot one. When all the books get bought, it would say that the shop is sold out when you try to buy but in reality, the unbreaking III book in slot one is protected from being bought because it's used as a reference and the shop would not know what to sell and buy without it. Is this correct?