You can craft various items at merchants' shops (the Fortune Teller, Blacksmith, and Inventor). When you order an item from a merchant by tapping the "Order" button it goes to a special crafting slot with a timer under it. Every item has its own crafting time that can be seen underneath it in the list. You can speed up this crafting time by paying rubies. To do this, tap the "Speed up" button under the timer. Each merchant can have up to two slots for crafting items. The second slot can be unlocked by paying 15 rubies.