The M7 was a blast mine that was used by the United States during World War II. Officially known as an anti-vehicle mine due to the fact that it was not able to penetrate a tank's armor, the M7 was placed by first moving the fuze into position, then removing the safety pin. It was then armed and activated by the means of a pressure plate. When the mine was activated, the pressure plate pushed a plunger down in order to smash a small glass vial of acid that then reacted with another chemical in order to activate the detonator.