Def attach
From The DarkMod Wiki
def_attach is used to attach an entity to another entity at spawning the first entity. This technique is for instance by the combined light entities.
Example
"def_attach" "light_candleflame" // The entity class we want to spawn and attach "pos_attach" "flame" // At the attach point called "flame"... "attach_pos_1_name" "flame" // ... which is defined here. "attach_pos_1_origin" "0 0 15" // Offset the flame X units in the Z direction
Optionally, you can set the rotation of the attached entity with:
"attach_pos_1_angles" "0 0 90" // rotated 90° around the z-axis