Attaching an entity to a bone.

I want to make it so a weapon when holstered is on the players back and i just cant get it to work, when ever i look up or down the weapon is parented/welded to the player but it still just moves away.
So i need it to be fully attached and stay attached to either the hip bone if its a pistol or the spine if its a larger weapon.

Thanks.

that would work great except for the fact that there’s at least 10 weapons holstered on the player at any given time

Obviously not in his particular mod.