Concrete masonry is losing projects to tilt-up, precast panels and steel frame at an alarming rate. Although masonry has many strong points, customers are swayed by advantages they often perceive in these other systems: lower installed cost, shorter site time and greater construction predictability. Market losses have accelerated in the past few years because innovation has significantly improved the other building systems, unlike block. As the history of innovation consistently shows, a successful innovation starts in a market niche. Innovative mortarless systems have improved with time and are now more competitive in many more market segments than before. Each of the six systems available in the United States was invented in the last 12 years, and each is well suited to one or two applications, where it competes effectively. One or more could be modified to suit other applications. All are useful here and now. Each mortarless system solves the problem of unit height tolerances differently. The Azar Dry-Stack Block system uses a stretcher and a corner. After stacking, crew members must check and adjust the wall back to plumb, using temporary bracing where necessary. Then they fully grout the wall, locking the plumbs into place. Haener Block have raised lugs, formed with a special contoured shoe during manufacture. The webs are offset from their conventional locations so that the lugs align and lock each block into correct position during stacking. The original system includes three block (a stretcher, a corner and a half). A new two-block system is available, which features a combined stretcher/corner and a half. The IMSI system produces an insulated, reinforced wall. It also has provisions for running electrical lines inside the wall. The IMSI stretcher has two rows of cavities. The outer row is for insulation and running wires. The inner row is for grouting, insulating and wiring where needed. The Sparlock system avoids the height problem altogether by placing block in a stack bond, where each block rests exactly on the block below instead of overlapping two units. So, if the block below are of different heights it does not affect the wall's plumbs or stability. Sparlock units interlock like puzzle pieces. Durisol block are made from a mixture of cement and mineralized-wood fiber, which create a material that is almost as durable as conventional concrete. It is easily cut with common wood saws and readily nailed with ordinary wood nails. Faswall, like Durisol, is made from a composite of cement and mineralized wood fiber that provides some insulation and is easily cut, and the block is designed to be reinforced and grouted to form a solid, structural wall. But the unit is sized to match a conventional full-dimension block in height and length (11½x8x16 inches). Each system currently has a modest but sustainable market share. Their inventors are working aggressively to expand usage and add new versions that will take their products into new markets.