GT Interface

Introduction
Gregtech is a large mod which adds a lot of complexity to the game; the learning curve is steep, but. This article covers the basic ways of interacting with the core functionality of blocks added by Gregtech. This includes configuring the way machines and pipes interact with things around them, applying and manipulating covers (as well as what covers actually do to the blocks you put them on), and understanding and using the graphical user interfaces (GUIs) of Gregtech machines (editor's note: if the GUI section gets too big, which it might, then it may be beneficial to split off into its own article). For practical use cases of pipes and covers, see GT Logistics (editor's note: I'm working on the GT logistics guide in tandem with this guide).

In-World Interactions
Editor's note: this section will describe: what different faces of GT blocks do and how to tell which face is which; how pipes and wires connect to each other and to blocks (and what kinds of blocks they can and can't connect to); how to access block faces with the wireframe visualization; how to apply and remove covers; in-world functions of GT tools; how to access different kinds of GUIs.

Gregtech Machines & Devices
One of the most common things in any Gregtech base will be singleblock machines: blocks which, when properly powered, will allow you to turn item and/or fluid ingredients into item and/or fluid outputs. These, along with other Gregtech blocks that have a wide variety of functions (e.g. transformers, item filters, hatches), are all capable of interacting with surrounding blocks in very similar ways and can be configured by the player in similar ways.

All Gregtech machines and devices can be safely mined using a Gregtech wrench.

Block Faces
For anyone unfamiliar with geometric terminology, a cube (in this case, a Minecraft block) has a surface composed of six squares called "faces". Most blocks in Gregtech (those with a function, anyway) have one unique face that is different than the rest. Singleblock machines actually have two unique faces. When you place a block, the unique face will usually be facing towards you.

The Wireframe
Certain Gregtech tools (the crowbar, screwdriver, wirecutter, wrench, and electric or multitool variants of these) as well as Gregtech covers and Railcraft crowbars (which behave identically to Gregtech crowbars) allow you to configure specific faces of functional blocks. When you hold any of these items and look at any Gregtech machine, functional block (like a transformer), pipe, or wire (or certain vanilla blocks, such as hoppers) at close enough proximity to interact with that block, you will see a wireframe overlay on the block face you are looking at. This overlay allows you to use the right-click interaction of the tool or cover you are holding to affect any face of the block without having to right-click the desired face directly. The face you interact with is determined by where you click on the wireframe. The image labelled "The Wireframe" is an example of how the wireframe overlay looks: it divides the block face into nine sections without obscuring your view of the block. The numbers are not present in-game; the screenshot has been annotated for the purpose of this guide. Right-clicking in the middle section (labelled "1" in the screenshot) interacts with the block face you are looking at, while right-clicking any of the corners (labelled "6" in the screenshot) will interact with the face opposite the one you are looking at. Right-clicking any of the edge sections (labelled "2" through "5" in the screenshot) interacts with the face immediately adjacent to the section that you click. For example, in the case of the screenshot, right-clicking on any of the sections labelled "6" interacts with the back face of the machine (since the player is looking at the front face in this case), right-clicking on the section labelled "3" interacts with the right face of the machine, and right-clicking on the section labelled "5" interacts with the bottom face of the machine; the latter is true even though the bottom face is completely blocked off in this case, and is therefore not directly accessible without breaking blocks.

Singleblock Machines
Singleblock machines have a front face (which has an identifying texture indicating the type of machine) and an output face (which has a dark grey square texture in the middle) (Editor's note: add screenshots). When you place a singleblock machine, the front face will be horizontally facing you and the output face will be opposite the front. The category of "singleblock machines" excludes things like generators and steam boilers, which are covered separately.

The front face can only be repositioned by breaking the machine and re-placing it. Covers cannot be attached to the front of a singleblock machine, and nothing can be transferred in or out of the machine via the front face by any method.

The output face can be repositioned to any other face (aside from the front face, which cannot coincide with the output) by right-clicking on the appropriate section of the wireframe layout using a Gregtech wrench. Gregtech singleblock machines can be set to auto-output items and/or fluids that are the products of recipes with a button in the GUI (see GUI section of this article), and this type of built-in auto-output occurs via the output face. By default, items and fluids cannot be inserted into a machine via the output face; this behaviour can be changed by right-clicking the output face with a Gregtech screwdriver to allow input via the output face (you can change this back to the default by simply right-clicking again on the output face with a screwdriver).

On steam machines, the "output" face instead serves as the steam vent; this means that the face must not be obstructed (i.e. the block space immediately adjacent to the steam vent face must be empty) in order for the machine to function. Steam machines lack an auto-output function for recipe products.

Singleblock Boilers & Generators
Gregtech's singleblock steam boilers are an exception to the rule of being unable to input resources via a machine's front face. Fuel-burning singleblock boilers can accept water via any face, including the front, though they cannot accept solid fuels via the front face. Fuel-burning singleblock boilers will automatically output steam to any pipe or fluid inventory connected to any face other than the front and bottom faces. This means that the front and bottom faces are usually the best places to connect water pipes to, as the boiler will never fill an empty water pipe with steam in such a configuration.

As of GTNH version 2.3.3, the high pressure lava boiler has special I/O functionality. Lava boilers will auto-import lava via the top face, and will auto-output steam via the back face. Water may only be piped into a lava boiler via the left or right faces. The new obsidian waste product of lava boilers may be extracted via the bottom face, and the front face is inaccessible to I/O methods.

Solar steam boilers have an output face resembling that of singleblock machines. This output face (which cannot be on the top or bottom) will automatically output steam, and is the only valid steam output of a solar steam boiler. Solar steam boilers can accept water from any face, including the steam output. These boilers also have a special top face, which must have a clear line of sight to the sky in order for the machine to generate heat during sunny conditions; any solid block will obstruct this line of sight, but non-solid blocks (including pipes, unusually) do not obstruct it.

Singleblock electrical generators (such as steam turbines or combustion generators) have a special face for outputting power, and this output can be repositioned to any other face by right-clicking the appropriate part of the wireframe overlay using a Gregtech wrench. These generators also have a special identifying texture on one or more faces, but the identifying texture is purely visual and do not impede any I/O methods.

Covers Overview
Editor's note: this section will describe all forms of covers and what they do to blocks they are placed on.

Graphical User Interfaces
Editor's note: this section will describe how to understand and interact with all Gregtech GUIs as well as the multiblock recipe display in NEI (since that is different than actual multiblock GUIs).