High Quality Content by WIKIPEDIA articles! Multi-jackbolt tensioners (MJT) provide an alternative to traditional bolted joints Rather than needing to tighten one large bolt, MJTs use several smaller jackbolts to drastically reduce the torque required to attain a certain preload. MJTs range in thread sizes from 3/4” to 32” and can achieve up to 20 million pounds of force and greater. MJTs only require hand-held tools, such as torque wrenches or air/electric impacts, for loading and unloading bolted joints.