Salt has long been used across cultures as a simple but deliberate form of protection placed at the threshold—the point where outside becomes inside. In European, Latin American, and folk Catholic traditions, it marked a boundary meant to resist spiritual intrusion, disruption, or unwanted influence. More than superstition, it was a practical system of awareness, repetition, and control over entry points within the home. This article explores how salt functioned as both a physical and symbolic line, reinforcing the idea that protection was not automatic—it was maintained.