Prefabs? Easy.

What's a prefab?
Answer: It's a collection of brushes and patches that together make some sort of prefabricated object that's something you'd like to use over and over throughout an area in the creation phase of a current and/or future map. A prefab can be a column, an arch, a room, a cabin, a sign, virtually anything.

How do prefabs work?
Answer: There's two ways to make a prefab:

1. Select the associated brushes and patches, and save them as a map file in a folder like baseq3/prefabs.
2.Or you can possibly (depending on your version) export the selected brushes as .pfb files which is basically the same thing.

Once you're ready to use the prefab, just import it and place it, then dupe and re-use throughout.