The crook is a tool used to break leaves and increase the chances of getting saplings, apples, and silkworms as item drops. The fortune enchantment can be used on crooks to increase the number of these drops. The crook is also compatible with the vein miner mod to break all leaves surrounding the one you broke and give you all the items you would have received normally.
Crooks can be made with stick, sugar canes, or bones to produce a crook of their respective type.
Crafting:
A hoe with only sticks.
Crafting recipe picture