OK, hi there. This has already been done, but this tutorial includes some of the finer details that Jered missed out in his (Still pretty good) tutorial. First steps to making a prefab. You need to either:

1. Find a piece of architecture in a level that you want to use in other levels (Or want to make available for other people to use in their levels)

or

2. Create something for over people to use in their levels.

[-----]

Well, after you've done either of the above, you need to take the following steps:

1. Boot up DXEd and find your object. Move the prefab-to-be away from any other brushes or parts of brushes. A big open space is a good idea. Also, try to make sure there are no other entities besides the object to be prefabed around. (IMPORTANT: Please note that you CANNOT prefab stuff like plants or people unless they are made from brushes. While it might be fun to include a Maggie Chow in every crusher prefab, >:), it is not possible. Also, movers cannot be prefabbed, although they can be MADE from prefabs)

2. Find a brush that is NATURALLY (I.E. Not expanded using the enlarging tools) larger than the entire object about to be prefabbed. This is important otherwise the brush will be truncated when you try to import it into the level. It happened with the UC when people tried to import it.

3. Move the VLB (Very Large Brush) over the thing you want to prefab. Make a final check that nothing besides the object you want to prefab is inside the radius of the VLB.

4. Time for the magic. Press "Intersect with World"...

5. ... and hopefully the red outline of the active brush will change to the shape of your object. If it doesn't, check you've done all the above steps correctly. If it does, proceed.

6. Go to Brush->Export Brush in the menu bar. Save it as a .t3d. Then you can use it in your levels, or, put it in a zip with a bunch of other ones and create a prefab collection.

7. NOTE: Do NOT claim that any prefabs you take from DX levels are yours, because it's rather lame and it's also quite obvious that it's not.

There is one problem with the above method, however. The intersection process merges all the brushes into one, which means you cannot seperate the shapes making up the whole object, which can lead to problems. Also, it can really muck up the game's physics if you turn the brush semisolid.

Also note the fact that the intersection process cannot understand semisolid brushes, so the entire brush will be wholy solid.

Another way to make prefabs is to find just one brush, selecting it, right clicking it and telling the active brush to imitate its shape. This is extremely unweildy, as it can only copy ONE brush at a time. However, it does mean if you copy all the brushes you can asemble the prefab from different parts, which allows you to be more precise with semi-solidness or placement of objects.

There you go. Have fun making prefabs, and don't be scared to fool around with some of the prefabs, see what you can piece together. Creativity is the first step forwards.