Hopper

While it appear deceptively simple (it's basically a box with a hole in it), the Hopper allows the construction of many advanced mechanisms. Any items that fall into the top of the Hopper are added to its inventory. If the Hopper receives Mechanical Power through axles mounted to its sides, it will begin to eject items from its inventory (and stop when the power is cut) out the spout below. Items may be ejected into the air, or directly into any other Block that has an inventory (chest, dispenser, cauldron, etc.), and it is also capable of eject its contents into a storage minecart parked beneath it. Also, if all the slots in its inventory contain items, it will send out a redstone signal warning that it is getting full (the signal will stop when there is an empty slot in the inventory).

Crafting

Wood Plank		Wood Plank
Gear	Wooden Pressure Plate	Gear
	Wood Plank

Filtering

The Hopper also contains an extra inventory slot in which you may place various items that act as a "filter" on which items it will swallow. Filtering hoppers can be placed in a trench so water will wash Items/Drops over every hopper. The water must decend one block after each hopper to avoid jamming.(Changed in 2.61 the trench can be on one level now)

Filter	stops	passes	passing Examples
Ladder	blocks	Items
Trapdoor	max. Stack<64	max. Stack=64	coal, torch, redstonedust
Grate	large Items	small Items	feathers
Wicker	not powdery	powdery	gunpowder, flour
Roller	Thick	Thin	string, paper

Note that the Hopper will not eject clay balls if they are placed inside of it (it gets stuck to the sides). As such, clay balls can be used as a "filler" within the Hopper inventory, allowing you to control precisely how much space is available to store other items within it.

You can also use the Wicker to separate gravel into flint and sand when used as a filter on the Hopper. <youtube v="MU5V2fePHzc" />

Applications

• Automated Chest loading
• Automated Drop sorting
• Automated Refilling of any Block that has an inventory
• Automated storage-mine cart loading

Keep in Mind

• The Redstone signal the hopper emits if no empty slot is available will reach the block beneath it. So a booster rail will be powered if the hopper is becoming full. To stop the minecart from escaping and causing the hopper to spill its content into the air place a block dispenser so it can place a solid block next to the booster rail. With this design you can trigger the minecart when the hopper has been cut from mechanical power.
• You may place multiple hoppers into one trench without incline. But to keep the Items/Blocks separated put another block between each hopper.
• Hoppers can catch fire and thus be destroyed.

Demonstration Video

<youtube v="4x1kj5UBMs8" /> <youtube v="RBnMLAKdm14" />

Auto Storage

<youtube v="PLItdsTFl4M" />

Full filtering list (WIP)

Name	Ladder	Hatch	Wicker	Grate	Roller	Soulsand
Flour/Hemp fibers/ Feather/Mushrooms	Yes	Yes	No	Yes
Bones/Sugar cane/ Leather/String/Foul food	Yes	Yes	No	No
Seeds/Gun powder/Redstone	Yes	Yes	Yes	Yes
Chop/Fish	Yes	No	No	No
Donut/Egg	No	No	No	Yes
Rope/Torches	No	Yes	No	No
Sand	?	?	Yes	?
Gravel	Yes	Yes	Yes (1)	Yes	Yes
Flint	Yes	Yes	No	Yes	No
Clay Ball	Yes	Yes	No	Yes	No
Redstone Torch	Yes	Yes	No	No	No
Gear	Yes	Yes	No	No	No
Dung	Yes	Yes	No	No	No
Redstone Dust	Yes	Yes	Yes	Yes	Yes
Diamond	Yes	Yes	No	Yes	No
Glass Block	No	No	No	No	No
Wooden Plank	No	No	No	No	No
Panel	No	No	No	No	No
Moulding	No	No	No	No	No
Redstone Repeater	Yes	Yes	No	No	No
Iron Ingot	Yes	Yes	No	No	No
Stick	Yes	Yes	No	No	No
Hatch	No	No	No	No	No
Sword	Yes	No	No	No	No
Bow	Yes	No	No	No	No
Arrow	Yes	Yes	No	No	No
Pickaxe	Yes	No	No	No	No
Coal	Yes	Yes	No	Yes	No
Bucket (Water)	Yes	No	No	No	No
Watch	Yes	Yes	No	No	No
Ladder	No	No	No	No	No
Stair (Cobblestone)	No	No	No	No	No
Dirt	No	No	No	No	No
Stone	No	No	No	No	No
Cobblestone	No	No	No	No	No
Bone	Yes	Yes	No	No	No
Platform	No	No	No	No	No
Slab (Wood)	No	No	No	No	No
Slime Ball	Yes	Yes	No	Yes	No
Feather	Yes	Yes	No	Yes	No
Bonemeal	Yes	Yes	Yes	Yes	Yes
Hemp Fibre	Yes	Yes	No	Yes	Yes
Fabric	Yes	Yes	No	No	No
Gold Ingot	Yes	Yes	No	No	No
Rope	Yes	Yes	No	No	No
Light Block	No	No	No	No	No
Sugar Cane	Yes	Yes	No	No	No
Wicker	Yes	Yes	No	No	No

Notes

(1) Gravel through the Wicker will separate into Sand and Flint, with flint not passing through the hopper and being left on top.