Hi folks,

Sorry i'm not really sure that I am posting this in the correct place, but any help would be much appreciated.

What I'm trying to do is import an STL file, then take a cavity in the shape of my STL out of another solid.

I can import the STL using a very handy plugin that I have downloaded, but when I try to use the subtract tool, i get an error that the STL is not a solid (is this beacuse I have surfaces inside the STL?)

Can anyone give me some pointers on how to make my STL a solid?

Any help or suggestions would be great, and appologies again if this is the wrong place to post these questions.

Thanks
Iain