BooleanUnion error?

I try to BooleanUnion 2 objects, they will make 1 object disappear.

Attached file:
tutorial 3 v1.3dm (328.5 KB)

Hello - yep - this is how Boolean operations work when open objects are involved - see help for more info-


Hi @pascal
I use Cap command to make Closed Solid. BooleanUnion work well.

Thank you