Prefabs FAQ

A list of (simple) questions about prefabs are assembled  and answered below by Shadow and bobzilla for the community.
I suggest anyone new to mapping or using prefabs should have a look at this.
1. What are prefab files for?
The primary reason for prefabs is to be able to create/construct simple or complex objects/brushes and have a library of these to use in multiple maps/projects.
An example would be to create a hanger complete and save as a prefab. Then when you are building your map,  you can use the "load prefab" to add/place in your map multiple hangers, being
able to rotate and position as needed.
Radiant only allows you to have one .map file open as you the only way to get pre-built objects into your map is to use the load prefab and place.
2. How can you use prefab files (in a new map and/or en existing map file)
Simple use the load prefab, from menu, and show where your prefabs are located. I keep all of my prefabs in a folder called "prefabs".
3. Can you ALWAYS change the .pfb extension to .map?
Yes, if you need or want to do this you can. You can then save it as a working .map or save as a prefab (pfb extension).
Remember, you can only load a prefab, not open directly. Changing the extension to .map allows you to open in Radiant.
4. Does this also mean you can convert (ANY) .map file back to .pfb extension?
Yes you can do this. Any of your work, big or small can be saved. Just hightlight or select the object/brushes, etc. and save prefab.
5. Would any prefab work for every game (AA/SH/BT)? Even when it's originally made for e.g. AA.
Most all prefabs will work in all version of the game. What does not work is sometimes the textures (if applied) that may be missing.
For instance. A mapper may have used a texture from the Spearhead or BT pack, and when a person tries to open or load in AA, the texture will be missing.
The mapper can re-texture as he deems fit. Remember that in Spearhead mapping, every player who run game in spearhead can see both AA and SP textures.
If the mapper is making for BT, some textures may be missing for AA and SP, because not EVERYONE bought or has BT installed.
6. How does someone make a prefab file? How is it created?
Create a prefab just like you making a map. Merely save as prefab from file menu and save in your prefab folder.
7. How can you view a prefab file? (see the 'model' and take a screeshot of it for example) and are there multiple ways to view them or just radiant?
You can only view files in radiant. Load the prefab into a blank map, and take a screen shot. You could rename your prefab extension to .map, open in radiant, take screenshot, quit and rename back.
8. How is the .map file from an actual complete map different than that of a .map file for a prefab?
A complete map may contain much other items, brushes, terrain, and objects. Just think of a prefabs are merely small or pre-built objects  that helped you get your map completed.
9. How can I load a prefab into my own map?
- Go to load Prefab and load one, when it loads and is still highlighted load your map that you wish to place it in, it will ask you if you want to copy the selection, click yes.
- Draw a square around entire prefab, go to select, and select complete tall, copy it then go o your map and past it, then move where you want.