Czech hedgehog The Czech hedgehog ( ) or ježek , 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 is very effective in keeping tanks from getting through a line of defence . It maintains its function even when tipped over by a nearby explosion . Although it may provide some scant cover for infantry , infantry forces are generally much less effective against fortified defensive positions than mechanized units . History . The Czech hedgehog ' s name refers to its origin in what is now the Czech Republic . The hedgehogs were originally used on the Czech - German border by the Czechoslovak border fortifications - a massive but never - completed fortification system built on the eve of World War II by Czechoslovakia . The fortification system fell to Germany in 1938 after the occupation of the Sudetenland as a consequence of the Munich Agreement . The Czech hedgehog was widely used during World War II by the Soviet Union in anti - tank defence . They were produced from any sturdy piece of metal and sometimes even wood , including railroad ties . Czech hedgehogs were especially effective in urban combat , where a single hedgehog could block an entire street . Czech hedgehogs thus became a symbol of " defence at all cost " in the Soviet Union ; hence the memorial to Moscow defenders , built alongside M - 10 in 1966 , is composed of three giant Czech hedgehogs . However , in some forms of warfare , Czech hedgehogs proved to be less effective . They were often made larger than they should have been , and although they were quite useful in urban warfare , there was little use of German armour in urban warfare in Russia . Czech hedgehogs were part of the defences of the Atlantic Wall and are visible in many images of the Normandy invasion . Technical details . A Czech hedgehog made to specifications could be constructed from any material capable of withstanding at least , while being at most high . However , such parameters were hard to achieve in makeshift hedgehogs , reducing their usefulness . The hedgehog is not supposed to be an immovable obstacle because of its size or weight . The proper size is to be slightly larger than the clearance under the enemy tank , so that a tank that attempts to move the hedgehog would instead roll on top of the hedgehog and get stuck . Industrially manufactured Czech hedgehogs were made of three L - shaped metal brackets ( L 140 / 140 / 13 mm , length , weight ; later versions : length , weight ) joined by sheet metal , rivets and bolt s ( or , later in the war , welded together ) into a characteristic spatial three - armed cross with each bar at right angles to the other two . ( This pattern forms the axes of an octahedron . ) Two arms of the hedgehog were connected in the factory , while the third arm was connected on - site by an M20 bolt . The arms were equipped with square " feet " to prevent sinking into the ground , as well as a notch for attaching barbed wire . During the Normandy Invasion the allies cut up several hedgehogs and welded them to the front of M4 Sherman tank s and M5 Stuart tank s . Known as the Rhino tank , it proved very useful for clearing the hedgerow s that made up the bocage s across Normandy .