Merging an entity's bones with another entity.

So, you know there is an addon named PAC, and there is an option to merge bones of the part with the player’s bones (align them). I’ve been wondering what is necessary to achieve the same effect without having to directly use BuildBonePosition to set the positions and angles manually. So, if anyone would kindly explain how it’s done, I’ll be really grateful.

From Flapadar: [lua]ent:AddEffects(EF_BONEMERGE)[/lua]