Subassembly

A subassembly is a pre-designed set of parts. The player can design these in the Vehicle Assembly Building or Space Plane Hangar. They are a great way to reduce construction and design time, by giving the ability to save complex blocks of parts, like big liquid-booster-stages with separately disposable tanks. A root node of a subassembly needs at least one empty stacked attachment node, where the subassembly can be attached to later rockets. A subassembly can't be used as the first part. All subassemblies are shared between both buildings but not between save games.

They were introduced in version 0.22.