The general and most popular plan was to place a charge of from 25 to 50 kilograms of perdit in a container within the entrance of the dugout, and connect it with the igniter and instantaneous fuse. These igniters were so placed that when any pressure was exerted on the step, it exploded the charge.
Usually, in the case of the 155-millimeter mines, about two feet of instantaneous fuse connecting the detonators, which were spring by pressure on the supporting blocks, were used.
This box had a yoke and a trigger connecting four igniters which, in turn, connected with four detonators and then, to instantaneous fuses. A pressure of some 40 or 50 pounds on the yoke would cause the explosion.