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Boolean operations let you combine or subtract shapes to create geometry that would be difficult to draw directly. CADit provides three boolean operations: Union, Cut, and Hole Material.

Union

Union merges multiple shapes into a single solid object. The resulting shape contains all the area covered by the original shapes.

When to use Union:

Combine separate shapes into one printable object
Merge overlapping shapes to clean up your design
Create complex silhouettes from basic shapes

How to use:

Select two or more shapes using the Transform tool (hold Shift to select multiple)
Open the context menu (right-click or tap the menu button)
Select Union

The selected shapes are replaced with a single merged shape. The new shape takes on the color and properties of the first shape you selected.

Union behavior

Union only works with filled shapes (not outlines)
Non-overlapping shapes become a compound shape with multiple parts
Holes within shapes are preserved where they don't overlap with other shapes

Cut

Cut subtracts the selected shapes from all other shapes they overlap. Use Cut to carve pieces out of existing shapes.

When to use Cut:

Create notches or cutouts in shapes
Remove material where shapes overlap
Carve details into larger shapes

How to use:

Draw the shape you want to use as the cutting tool
Position it over the shapes you want to cut
Select the cutting shape
Open the context menu
Select Cut

The cutting shape removes material from every shape it overlaps. The cutting shape itself remains unchanged.

Cut vs. Hole Material

Cut is a one-time operation that permanently modifies the underlying shapes. Hole Material (described below) creates a persistent cutting relationship that updates automatically when shapes move.

Hole Material marks a shape as a transparent cutter. Hole shapes cut through all geometry they overlap, creating through-holes in your design. Unlike Cut, Hole Material is persistent: if you move a hole shape, the cut updates automatically.

When to use Hole Material:

Create screw holes or mounting points
Add ventilation slots
Make windows or openings that cut through multiple layers
Design interlocking parts

How to use:

Draw the shape you want to become a hole
Select the shape
Open the context menu
Select Toggle Hole Material

The shape becomes transparent with a striped pattern, indicating it will cut through any shapes it overlaps. Toggle Hole Material again to convert it back to a solid shape.

How hole shapes work

Hole shapes appear transparent in the 3D view
They cut through all solid shapes they overlap, regardless of height or layer
Moving a hole shape updates the cuts in real time
Multiple hole shapes can overlap to create complex cutouts
Hole shapes do not appear in the final exported model

Hole shapes in Doodle Mode

In Doodle Mode, hole shapes work across all layers. A single hole shape can cut through shapes of different colors stacked above it.

Choosing the right operation

Goal	Operation
Merge shapes into one object	Union
Remove a piece from specific shapes once	Cut
Create a hole that always cuts through overlapping shapes	Hole Material
Make repositionable cutouts	Hole Material

Tips

Before using Union, make sure all shapes you want to merge are filled (not outlines).
Use Hole Material for mounting holes that need to align with other parts. You can adjust their position and the cuts update automatically.
Hole shapes are useful for creating cookie cutter edges. The hole cuts through the base, leaving raised walls.

Boolean Operations