Parallel objects, also known as shell objects, can be created from other objects, either on just one side or on both sides of the original objects. These are called single and double parallel objects, respectively. This unique operation of form·Z allows you to transform a volumetric model of a building into one with walls that enclose space, and to transform a surface object into a shell with thickness.

A parallel object is derived from a volumetric composition, creating a walled enclosure.

Left to right: A meshed dome is created using three control lines, then a double parallel object is generated from it.
The original object can be a solid, a surface, or even an open polyline. Parallel polylines can be further articulated, and can then be meshed to derive freely flowing objects such as ribbons or flags.

Left to right: Parallel lines are generated from an original 3D polyline. After some further articulation of the lines, they are used to generate a freely unfolding ribbon.