Three-prong plugs incorporate a ground pin that connects exposed metal parts to the wiring system ground. Two-prong plugs do not have a grounding pin. Such appliances include power tools. Removing this pin could lead to electrical shock. Polarization is primarily used to reduce the potential for shock.
Consumers can identify polarized plugs by one blade being wider than the other.
Older homes may not have polarized receptacle outlets. If not, the receptacles will not accept polarized plugs. A qualified electrician should replace the old receptacles and put in wiring consistent with polarization. Do not risk injury or fire by modifying or forcing the plug blade to fit into the outlet. The switch is the point where two worlds meet-human and electrical.