The UnionOperation combines parts together into a single solid model. To use it, select the parts you want to combine and click the Union button in the Model tab. This will create a new part called Union.
This function can be used in conjunction with NegateOperation to shape, resize, and create holes in solid models. Combined parts can also be separated, allowing developers to revert (undo) the result of a unioned model.
You should only use Union on basic parts (block, sphere, wedge, or cylinder). Also, these parts should not have any children such as scripts, surface GUIs, etc. If a part with children is unioned, the children will be hidden from the DataModel.
- Solid modeling, an article that dives into solid modeling