Building Gadgets is a mod by Direwolf20 that adds several tools that make building in Minecraft very much easier.
[You can read the official wiki for the mod by clicking here](https://github.com/Direwolf20-MC/BuildingGadgets/wiki)
All Gadgets need RF to function.
Hold the mods's Settings button (G by default) to open the radial menu:
The radial menu has all the different settings for the Tools. On the Building Gadget, each of the buttons on the circle are a different building mode, the buttons on the right are options for that building mode, and the buttons on the left are for manipulating the world.