This file assigns the kits possible to be used by given race in given class as defined in KITTABLE.2DA.
The filenames of these files are constructed as follows : K_(first letters of class name)_(first letters of Race names).
Standard identifiers are as follows:

Class abbr. Class name Race abbr. Race name
F Fighter H Human
C Cleric D Dwarf
T Thief G Gnome
B Bard E Elf
P Paladin HE Half-Elf
D Druid HL Halfling
R Ranger HO Half-Orc
FM Fighter Mage    
FC Fighter Cleric    
FT Fighter Thief    
FMT Fighter Mage Thief    
MT Mage Thief    
CM Cleric Mage    
CT Cleric Thief    
FD Fighter Druid    
FMC Fighter Mage Cleric    
CR Cleric ranger    
S Sorcerer    
MN Monk    
BN Barbarian    

Files description:
First column of these files is number on the list.
Second column consists list of kits numbers from KITLIST.2DA that may be used in the given class/race combination.
In BG2 ToB we have for example K_C_HE.2DA (file for Cleric, Half-elf):
2DA V1.0
1	0
2	19
3	20
4	21