A line in space with a direction: an origin and a unit direction, such as the axis of a cylinder.
The axis as a Solid, built from the distance to its line.
The axis's unit direction.
A point the axis passes through, used as its origin.
Distance to the axis line as a field; zero on the axis.
Items that are each an Axis. One Axis wired where a list is taken counts as a list of one.