A friend asked me the other week what these were called in English. All I could think of was "concrete jacks" as that's what I think they resemble. Koreans use these as part of their sea walls, and since Korea is always trying to reclaim land, they're everywhere. They're quite large, as from what I've seen only two can fit on the back of a flatbed truck. They interlock fairly well and look better than a solid concrete slope, so I vote we start to use them in America.