Q. What's this mod all about?

A. It's pretty simple. Hoppers can't transport items upwards. This mod adds ducts, which can attach to hoppers and send items in any direction. This mod also now adds Grated Hoppers, which can filter items.

Q. What's the difference between a hopper and a duct?

A. A few things:

Ducts can send items into inventories above them.
Ducts won't pull items from inventories above them.
Ducts only have a single inventory slot.
Ducts can be pointed in a different direction after placing them by hitting them with a stick. Left-clicking with the stick cycles through all possible directions, right-clicking with it cycles in reverse. You can also shift-left-click with the stick to reverse if you prefer. When in creative mode, however, only right-clicking will be available, as left-click breaks blocks.
Ducts auto-orient to adjacent ducts or hoppers. Hold the sneak key while placing to disable this behavior.
Ducts have smaller hitboxes, making it easier to reach blocks behind them.

Q. Then what's a Grated Hopper do?

A. Grated Hoppers contain an extra row of items in their interface. This is the filter inventory. Only items matching this row are allowed into the hopper from a chest, hopper, or duct above it. The Grated Hopper will also only eject these particular items into its destination. Finally, it prevents a hopper beneath it from removing items matching the filter.

Items can still be inserted into the Grated Hopper from the sides and bottom which do not match the filter. This means that you can insert anything into a Grated Hopper, have it eject its matching items into its destination inventory, and then have regular hopper or Grated Hopper beneath it, pulling out the items which don't match the filter, to be directed elsewhere.

Q. What are the crafting recipes?

A. Hopper Ducts are a reduced version of the hopper recipe:

Grated Hoppers are a shapeless recipe:

Q. What do I need to run it?

A. You'll need at least Minecraft 1.6.2 with Forge 804 or greater. It uses SRG, so it will possibly work on future versions of Minecraft as well. It's tested to work with 1.6.4.

Due to requests, this mod has also been backported to 1.5.2. That version was built using Forge 738. Note that versions for 1.5.2 may not be up to date with the latest release for 1.6.x.