This is aimed at new users of Sketchup like me. When doing something like a house with a lot of detail it is a good idea to make various parts of the model, say each wall of a room or the verandah or support columns, a component. The good thing about doing this is that it doesn't stick to the other parts of the house it is in. This makes it easier to make changes to the house design or to the component itself. If there a lots of copies of the component simply modifying a copy of the component and saving it under the same name will change all the copies at the same time.
Components can be joined with other components to form a super component, say the roof of a garage or even the whole garage. Models downloaded from the Google 3D Warehouse are made up of components. Just explode them to make changes, then make them a component again (by having all parts selected then right clicking and choosing Make Component).
Not making components means that deleting a line for one bit you don't want may wreck another part that is attached (glued) to the unwanted part.
I have just realised all this through experience while doing a paying job for the first time with Sketchup over the past couple of weeks.
Handy Hint for easy changing of models
Re: Handy Hint for easy changing of models
Thanks for the tip Jeri3d