4 was a landmine used by the United Kingdom and other Commonwealth countries during World War II.
The bounding mine‘s sides and bottom are made of concrete and shrapnel.
[1] The mine's container is buried in a hole with a small amount of loose soil on top making it appear invisible.
[1] Detonating the mine begins with a compression of the pressure switch, collapsing an igniter ampule in the tube.
[1] This lights a connected fuse that burns to the middle, triggering a black powder charge out just under the bounding mine in its container.