This command can be used to determine where a line projection would intersect a target surface. You can select a start location (Coordinate and Elevation) and a Bearing (use SHIFT Click on the line to determine the bearing of the line) and the Vertical Angle (Again use SHIFT Click to determine the Vertical Angle of the line) and it will project the line at the same Bearing and Vertical Angle till it intersects the target surface model creating a point at the intersection.
You can also create multiple points or a 3D linestring where the same VA but with a varying bearing (computed from the number of points required e.g. if you type in 4 points you will get a triangle, if you enter 5 points you will get a square (projected to a flat surface), if you use a large number of points you would get a circle (on a flat surface) - but if the surface has varying elevations you will get an irregular shape result. See the video