Section 26(6)(a) in The Dock Workers (Safety, Health And Welfare) Regulations, 1990
(a)If the fixed holds ladders cannot extend upwards on to the coamings, strong cleats shall be fitted to the coamings in the same line as the ladders at intervals not exceeding 30 centimetres having a clear internal width of at least 30 centimetres while affording free footroom of at least 12 centimeters and so constructed as to prevent the foot from slipping sideways: