For a typical 1000mm high wall, post holes must be dug at a minimum of 1100mm deep and 450mm in diameter. For larger walls, please check with relevant authorities via your council wherever permits and regulations apply. Steel posts should be set 15mm longer than the sleeper being installed (e.g. 2015mm for a 2000mm long sleeper). Fill holes with concrete and ensure all sides and underneath of steel is covered by at least 100mm. Concrete should finish 10mm below base of bottom sleeper. Once concrete has cured, place sleepers between steel posts. Once installed, place plastic membrane behind wall and slotted drain along length running to a discharge point.