Several main types of obstacles were built on the Normandy beaches to slow up landing invaders. They were organized into three basic lines.
The outermost line, found about 250 yards below the high water line, consisted of 'Element C' obstacles (pictured below). These were approximately 10 feet high, built of reinforced iron, and normally had mines attached to them.
The next line, 25 yards nearer the beach, consisted of wooden mined ramps (below). The explosives attached could be mines or artiilery shells.
Mixed among these were found mined stakes (below), again with mines or shells attached.
The final line was about 125-130 yards from the beach. Steel hedgehogs (below) approximately 5.5 feet tall were fixed in rows about 20 feet apart.
The extensive coverage of the beach obstacles can be seen in the following plate drawn from a Ist Division assault map, April 1944.
Illustrations above from: Operation Report Neptune, Omaha Beach Provisional Engineer Special Brigade Group, 1944.