Restrained Joint systems for Ductile Iron Pipes come in two main types. A bolted joint uses a socket hood, gland, split retainer ring and hook bolts, while a boltless joint uses a long two-chamber socket with locking bars. Both rely on a spigot weld bead and a standard push-on gasket, resist axial pull-out under high pressure and remove the need for concrete thrust blocks. Boltless joints keep 3° deflection up to DN 1000 and suit trenchless work, while bolted joints drop to 2° in larger sizes. Compare DI Pipes and DI Fittings to choose the right joint for your project.