Is the sewn part of an impure garment, such as plastic, leather, or metal, purified, even though water does not reach it directly except after passing over the fabric, or must it be opened to pour water on it?

If impurity affects a spot on a garment, its ruling does not transfer to the inner side or the opposite side unless there is certainty. If such certainty is not achieved, it suffices to purify the affected spot by pouring water over it. However, if there is certainty that the impurity has transferred to a specific part, then it is obligatory to immerse the garment in water until it reaches the impure spot, and there is no need to undo its stitching. One should avoid delving deeply and being overly meticulous in this matter to prevent obsessive thoughts (waswas (definition)).