Structure Extender

A Structure Extender block detects the block directly below it or the block directly above it, then extends the detected block in the opposite direction until it reaches the next solid block. A typical use is a chain that should run from a mineshaft-style structure up to the roof of a cave, where the block is placed on top and extends itself automatically. The block replaces itself during this process, and it only works when exactly one block sits below or one block above it, with air on the other side.

The mod was built for mod creators who make structures and want the process of placing long runs of blocks to be easier. Placing the block on top of a stack with at least one air block below it lets it extend up to 300 blocks of air. A gamerule named structureextenderactive can be set to false, so a builder can place the block first and activate it later, and a new world loads structure extender blocks as active without any extra step.

Installation is needed on the client and on the server, because the environment is client and server. Structure Extender is published for Forge and NeoForge, with files for 1.20.1 only, and the code is licensed under the MIT License.