How to prevent child objects to move ? I have created a light bulb and I want all the objects of the light bulb "behave as one entity". So I thought I should create an empty and make that empty the parent of all child objects (together the light bulb). But now it is still possible to select and move an individual child object. And I don't want that. If I select the glass and move that I want the whole light bulb to move. 

I want to build a library of 3D models and I want to be able to append a 3D model (for instance a light bulb) and move that model in my scene. But I do't want to join all meshes, I want the individual child objects to stay separate objects.
That is exactly what Dupli Groups are for.


Create a group that includes all the individual components.
Add this group as an instance into the scene: Add > Group Instance. This instance will behave like one object.
You can link a group from another file, which could represent that library you want to create. In the library file you have still access to all the groups components and you can edit them, but the linked instance will behave like one entity.


This has also other benefits like saving memory if you need multiple instances of the same group.