 Merrifield wished to design a block that did not break up or shift when struck by the sea; that was cheap; and that did not require precise placement.He said in later years that he wanted a block designed in such a way that it could be ""sprinkled like children's jacks"".Kruger stated that he went home for lunch, cut three sections from a broomstick, and fastened them with nails into an H-shape with one leg turned through 90 degrees to create the distinctive "dolos" shape.