The main process for joining the parts of a steel structure is by welding, although bolting is often used to connect the parts of  topside modules. Jacket type structures consist of tubular members welded together into a space-frame. The large diameter tubular legs, chords and braces are formed by rolling plate to a curved section and then longitudinally and circumferentially butt welding the sections with full penetration welds to create tubular sub-assemblies. The tubular subassemblies are connected at welded joints called nodes or nodal joints, which are critical for transferring and distributing the load carried by the structure. This chapter reviews the importance of welding, the main welding processes and bolting methods used for offshore structures.