Slope Block Mark IV Unilock is the authorized dealer and producer of this product covered under U.S. and Canadian Patents. Slope Block Mark IV is a split faced concrete retaining wall system that combines outstanding retaining characteristics, durability, natural stone appearance, design flexibility and the ultimate simplicity of construction. Slope Block Mark IV is used in a variety of applications; retaining walls, terraces, embankment, slope protection, and noise protection mounds. Slope Block Mark IV is maintenance free. The units do not require surface treaent and their high density, strength and specification standards are such that the units are not subject to dimensional change, distortion or cracking.