Admiralty Scaffolding

Admiralty scaffolding, officially designated Obstacle Z.1, was a British anti-tank and anti-boat obstacle built from tubular steel and erected on English beaches during the anti-invasion preparations of the Second World War, with some sections also built inland. Its most common form, Z.1, used steel uprights nine feet high spaced four feet ten inches apart, linked by horizontal tubes and braced diagonally into twenty-foot sections; these were first set at the half-tide mark to obstruct landing craft, and later moved up to the high-water mark to stop tanks. The effort was vast: Britain installed more than 15,000 miles of scaffolding tube, consuming half the country's scaffolding steel output, at an estimated cost of 6,600 pounds a mile.