Among the most important finishing structures of a vehicle interior, the door trim panels reduce external noises, present ergonomic concepts generating comfort, improve appearance, and provide objects storage, knobs and buttons. The panels usually composed of several molded parts (trim, armrest, etc.) connected to each other also have structural function as support closing loads, protect occupants of door internal mechanisms, energy absorption in side impacts and resist misuse conditions. Therefore, these trims usually made of polymeric materials must to present good structural integrity, demanding appropriate connections between components to have good load distribution. The connections between parts can be made using bolts, interference fits (like self-locking), welding tubular plastic towers (heat stakes), or clips (such as snap fits) and last two are the most common due to be cheap and with good retention. Compared to heat stake (most used type) snap fits are simpler, eliminate welding nest costs, make faster and more robust connection eliminating heat stakes welding process variations. However, it must have a suitable design with good retention and low clipping load to avoid ergonomic problems on production line. One of the main tools used for development of structural components, allowing determination of possible field complains, is the numerical simulation by the finite element method, an economically advantageous and efficient tool, which enables a design excellence. Through structural simulations it is possible determine retention and insertion snap fits loads, generating a robust product with quality and which meets customers required satisfaction levels.