The two surfaces in a contact definition should be touching in the assembled product. See About Proximity and Orientation Requirements.
Only the common interface of two surfaces connect during a simulation;
surface regions that do not overlap are excluded automatically from the contact
definition. Consider the two crossing bars in the following image (left). The surfaces
selected for contact overhang each other significantly (center). During the simulation,
only the regions of the surfaces that are touching are connected (right); the remainders
of the surfaces are free to move and deform independently.
