Trajectory ribs are most often used to strengthen plastic parts that include a base and a shell or other hollow area between pocket surfaces. The pocket surface and base must consist of solid geometry. Create a trajectory rib by sketching the rib path between pocket surfaces, or by selecting an existing sketch. The rib has a top and a bottom. The bottom is the end that intersects the part surface. The sketch plane that you select defines the top surface of the rib. The rib geometry's side surfaces extend to the next surface encountered. The rib sketch can contain open, closed, self-intersecting, or multiple loops.

A Trajectory Rib feature is one trajectory, which can include any number of segments in any shape. The feature can also include a round for each edge and a draft. You can define the draft, rounds, and rib width in the graphics window or on the Trajectory Rib tab. You can separate rounds as a standalone feature that can be redefined as another feature.

Trajectory rib edges and surfaces are grouped by type into intent objects. These include the rib side surfaces and different types of rounds.