General Jim's German Landing Craft Barrier Building Block Set Anti-craft Antitank Obstacles block playset (Set of 10). The proper name for these are Hedgehogs. They were usually made of steel angles or rails measuring approximately 1.5m and 2m in length; two pieces crossed in an X form with a third resting on an angle in the crossed rails; either bolted or welded together; positioned in shallow water and anchored with concrete bases. They were meant to hinder military advances of water landing craft by piercing the bottoms of the landing craft. They were also used to hinder the progression of small and medium tanks. Their shape made the effective even when tipped over . Compatible with all major building blocks. Great addition to your city themed building block bricks toy collection. 100% Satisfaction Guaranteed! No Builder Left Behind Guarantee: Have a problem with your order or need replacement parts? Please contact us through buyer/seller messaging. We strive for the best customer service! Product comes unassembled in original packaging with detailed printed paper instructions. General Jim's German Landing Craft Barrier Building Block Set Anti-craft Antitank Obstacles block playset (Set of 10). The proper name for these are Hedgehogs. They were usually made of steel angles or rails measureing approximately 1.5m and 2m in length; two pieces crossed in an X form with a third resting on an angle in the crossed rails; either bolted or welded together; positioned in shallow water and anchored with concrete bases. They were meant to hinder military advances of water landing craft by piercing the bottoms of the landing craft. They were also used to hinder the progression of small and medium tanks. Their shape made the effective even when tipped over. Compatible with all major building blocks. Great addition to your city themed building block bricks toy collection. 100% Satisfaction Guaranteed! No Builder Left Behind Guarantee: Have a problem with your order or need replacement parts? Please contact us through buyer/seller messaging. We strive for the best customer service! Product comes unassembled wrapped in original polybag packaging with printed paper instructions.