Hello i want to subtract my windows and doors but i face a problem

The problem is ‘One or more of the selected objects is either not a solid or is locked. The non-solid/locked objects will be de-selected before this operation is performed’. How can i fix that?
Untitled6.skp (488.0 KB)

Make them ‘solids’, as it says

Basics of SketchUp at learn.sketchup.com


it worked, thank you very much.

A solid is either a group or component, it must be a closed geometry without stray edges, internal faces and groups or components within the group. There is a plugin called solid inspector that can detect some of the errors that prevent an element from being a solid, some of them can be solved by the plugin and other errors must be solved manually, there are cases where it can get a bit confused depending on the geometry you have grouped so it’s not 100% accurate but for beginners it’s a good tool. There’s another plugin called fixit101 that can solve some errors that solid inspector can’t, like creating faces to have a closed element, and another that helps you to get a cleaner model called clean up, those three plug-ins together a a great bundle for beginners and even experts.