Projection - New Geometry
The projections tools under the New Geometry section of the Construction tab offer a set of options to build new geometry based on projecting objects from one to their intersection with another.
Project Line to Plane
After selecting a plane as the destination, you will be prompted to select the line you wish to project. A new line will be created on the projection XY plane of the selected plane. Effectively the end points are projected to their closest points on the plane and a line is then created between them.
Project Line to Circle
After selecting a circle as the destination, you will be prompted to select the line you wish to project. A new line will be created on the projection XY plane of the selected Circle.