The height of an obstacle would be just underwater at near high tide. They were angled and braced sufficiently to punch a hole in small landing boats that they knew would be used in a landing. Usually each had a "teller" mine attached, teller meaning dinner “plate” in German. They were placed to detonate from the pressure of the weight of the landing craft and were powerful enough to demolish the front-end steel door, kill several soldiers, and sink the craft immediately. The Czech hedgehog was a static anti-tank obstacle defence made of angled iron (that is, lengths with an L- or H- shaped cross section) deployed during World War II by various combatants. The hedgehog was very effective in keeping tanks from getting through a line of defence. It maintained its function even when tipped over by a nearby explosion. These Czech hedgehogs were taken up by soldiers after the landings on the Normandy beaches.
