Building tools, and undo

The six tools

The build tools sit in the Build tab. Pick one and it shows a short hint about what the next click does.

Tool	How to use it	What you get
Block	Place one block at a time.	A single piece, as in the normal game.
Line	Click where the line starts, then where it ends.	A straight row of blocks, drawn in three dimensions, so it can run up a slope.
Wall	Click the two ends of the bottom.	A wall as high as the Height setting, up to 32 blocks.
Box	Click two opposite corners.	A solid block of blocks, or with Hollow on, a room: walls, floor and ceiling only.
Circle	Click the middle, then the edge.	A ring a block thick, lying flat on the ground. With Hollow off it is a disc.
Fill	Click a wall, floor or ceiling.	The whole flat area you point at is covered, so you can paper a wall or tile a floor.

A tool works out where the blocks go. The blocks themselves are the same as the one you are holding, with the same shape, turn and style. Everything a tool lays at one time is one step, so one undo takes it all back.

Limits

• One tool lays at most 3,000 blocks at once. Anything past that is left out.
• A wall takes a height from 1 to 32 blocks.
• Fill covers at most 1,024 squares, and no further than 24 blocks from the square you clicked in any direction.

Symmetry

Press N to set symmetry. It cycles off, mirror across X, mirror across Z, and both. Symmetry mirrors each placement through the block you first aimed at, so a wall built on one side appears on the other. Shapes with a front are turned to match the mirror, and a corner stair is handed so the mirrored corner still faces the right way. Blocks sitting on the mirror line are not doubled.

Turning and flipping

R turns the piece you hold in quarter steps. F turns it upside down, which suits slabs, stairs and wedges. X mirrors the piece you are holding. Cables take a colour instead of a turn, chosen with the rotate key.

Undo and redo

Press Ctrl+Z to undo and Ctrl+Y to redo. Each player keeps the last 64 edits. Undoing a placement gives back the items it used. Undoing a break needs the item back in your bag. A whole tool lay, or a blueprint paste, is one step.

Tips

• Use Box with Hollow on for a quick room, then add a Fill across the inside walls.
• A Line along a slope lays blocks that step up with the ground, which is handy for a ramp.
• With symmetry on both ways, one wall build gives you four walls round a central point.
• Check the number before a big Fill. If it stops short, it has reached its square limit.

To copy regions you have already built, see blueprints and symmetry. For the pieces the tools lay, see building pieces and shapes.

← Back to the wiki · Last updated 25 October 2026. Mantlenaut is in alpha, so things change.