Tamping shall be done only with wood rods without exposed metal parts, but non-sparking metal connectors may be used for jointed poles. Plastic tamping poles may be used, provided they have been approved by the Division of Industrial Safety. The end of the tamping rod shall be kept square and of such diameter that the tamping rod will not by-pass the cartridges in the hole. When explosives are loaded into a bore hole, tamping shall be by pressure or light blows only and never by violent ramming.