This allows you to pick it up and carry it.
Set it up like you would a collision primitive using this naming convention:
p_-f_somename
Example: rep_fly_anakinstarfighter.msh
Hidden/Spoiler:
An 'Argument 0' error on export is typical when exporting primitives but this does not affect the exported msh.
For more information on how to set up collision primitives please see the art_guide.doc included with the BF2_modtools documentation.