Now most of this information was gained a long time back for UT2003 from another source of whom I know nothing about except it refers to a guy called Erik. If you want a more specific link Mr Erik, please tell me so I can give you the credit you are due and my praise for saving me many months in a comatose state of frustration and stress.

The 15 sockets are as follows, and cover most if not all of the needed information to get your character to work correctly in UT2004.

Note if your bone name has spaces in it, type your bone name within quotation marks (ex: "Right Shoulder"). And don't forget to apply the changes once done.

AttachAlias 		BoneName (in my instance)
righthand			Bone_weapon		
Weapon position

FlagHand			Bone_weapon		
Flag position

rshoulder			Bip01 R Clavicle	
Dismemberment location, Team Corona

lshoulder			Bip01 L Clavicle
Dismemberment location, Team Corona

rfoot				Bip01 R Foot
The flag for the right adrenaline speed trail. 

lfoot				Bip01 L Foot
The flag for the left adrenaline speed trail.

head				Bip01 Head
Used for the Big Head Mutator,head blown off, etc. Use your neck joint.

spine				bip01 Spine
when your torso gets blown off, and other stuff. Use one of your lower back joints.

rthigh			Bip01 R Calf
When your right leg flys off, catches fire, etc. 

lthigh			Bip01 L Calf
when your left leg flys off, catches fire, etc. 

rfarm				Bip01 R Forearm
Effects for your right forearm. 

lfarm				Bip01 L Forearm
Effects for your left forearm. 

The following are used for blending animation purposes. So if you want to get your character to work properly you need to add these. If your character is not blending properly (top half works but the bottom doesn't, legs work but the top doesn't etc.) then this is probably where the problem lies and can usually be fixed with playing around with the bone order.

Bip01				Bip01
Your skeleton's root bone.
 
Bip01 Spine 		Bip01 Spine
Highest Spine bone in your hierarchy.

Bip01 Spine1		Bip01 Spine1
Next spine bone in your skeleton.

Bip01 Spine2		Bip01 Spine2
Next spine bone in your skeleton.

Bip01 Head			Bip01 Neck
Your neck bone.