Snap-fits are preferred when mounting injection-molded plastic parts with complex geometries, locking them in place of chemical adhesives and screws. The use of Snap-fits is based on the accurate calculation of the interface and the associated coupling strength. In this study, a Modal Analysis process was carried out for the products obtained by using Polylactic Acid (PLA), Acrylonitrile Butadiene Styrene (ABS) and Polyethylene Terephthalate Glycol copolymer (PET-G) materials of a connecting element with locking detail on the movable, which is described as beam or movable. Harmonic Analysis was performed using the data obtained from Modal Analysis. The obtained data were interpreted.