Galvanized Vent Hole Plugs, whether Aluminum or Zinc, will seal themselves very tightly with normal installation. The slight taper in the body allows the plug to be driven into the hole like a wedge. Each successive hammer strike drives the plug in slightly further and makes it a little tighter. As well, both Aluminum and Zinc Vent Hole plugs are relatively soft, malleable metals. While being driven in, they conform to the minor irregularities of the hole. In this way with normal installation, the plug is sufficiently tight to remain in place for the life of the fabricated steel.