Intersections and developments are commonly found in many technical disciplines. Two surfaces that meet form a line of intersection. A pipe going through a wall is an example of an intersection. As an engineer or technologist, you must be able to determine the exact point of intersection between the pipe and the wall. A development is the outside surface of a geometric form laid flat. Sheet metal products are an application for developments. A cardboard cereal box, the heating and air conditioning ductwork used in buildings, or large aircraft, when laid flat, are examples of developments. As a technologist, you should be able to visualize and create the development of common shapes, such as cones, prisms, and pyramids. This chapter will address both traditional methods and CAD techniques for drawing intersections and developments.