New mortarless, stackable concrete block systems are answering the needs of the growing retaining wall market. Because these systems are mass produced in concrete block plants, controlled production quality and cost savings are possible. The block are made of high-strength, high-density concrete that resists erosion and cracking. Most systems are designed to last at least 50 years and require little or no maintenance. No special tools or skills are needed for assembly. Simple connection mechanisms, such as keys, lips, or pins, allow fast, mortarless erection. KEYS Keyed systems use block having interlocking tongues and grooves or top and bottom angle cuts. LIPS Some systems have block with protruding upper or lower lips that determine wall setback and prevent units from shifting forward. PINS Other systems use corrosion-proof fiberglass pins to connect units. The pins fit into preformed holes and extend down into the slots in the unit below. INSTALLATION BASICS Because these systems are self-aligning, accurate placement of the first block course is essential. For walls taller than 8 feet, most manufacturers recommend installing geogrid soil reinforcement. A geogrid is a mesh of corrosion-proof, high-density polyethylene.