It lets you continue flying with a double jump. Pressing the Fly button enables safety flight.You must set a keybinding for it to make travel. The keybinding package for Fly is not packaged by default.So, you can use it to locate torches or other sources of illumination in caves. The Cavefinder does not turn on Fullbright automatically, as XRay does.You can also build additional XRay profiles, and give them a primary in-game binding if you want more customizability.You can select the different blocks rendered in the user interface and the ones not rendered.
2 Minecraft Forge (Modding API) Installation Guide.