To project an element against a plane defined by two points

Select the Move as Projection tool.
From the Proj. Onto Plane Def. By option menu, choose 2 pts/view.
To define a line, enter two data points.
An imaginary plane is constructed through both points and perpendicular to the view of the first point.
Select an element to project. The projected element is highlighted.
To accept the new element, enter another data point anywhere.