Minecraft wiki entry for Anvil_mechanics, associated text: To minimize the prior work penalties, always combine two items with equal penalties as possible. It is possible to have 7 different enchantments on a single pair of boots. Starting with an unenchanted pair of boots and the 7 enchantments on individual books, the limit on the cost permitted by the anvil is exceeded if trying to combine the books one at a time with the boots. However, it is possible to avoid this by properly pairing up the items. First combine the boots with one of the books, plus the remaining 6 books in 3 pairs. Then combine the boots with one of the books and the other two books that have 2 enchantments each. Finally combine the boots with the book that has 4 enchantments. This results in a pair of boots with 3 workings on it, although in practice 7 workings have taken place.