An Alpa lock is a safety lock which can be used for earrings, and comprise a spring-loaded mechanism that is activated when you apply pressure to it. By pushing the two small buttons on either side, the lock can be inserted or removed easily.
By using an Alpa lock, earrings cannot fall out because they will slide into a small gap when retracting. They're designed to provide a comfortable and secure fit that can be quickly and easily adjusted.