As we read on the Lwówek police fan page:

The international “help me” sign is a discreet signal that we can send to someone we know or to a complete stranger. It informs them that we are victims of violence. However, we cannot resist or loudly call for help. As a result, we could face severe punishment from our abuser, with whom we live every day.

The officers add:

Many people become victims of domestic violence, and the pandemic has additionally meant that we have nowhere to escape. Victims of domestic violence are often left to fend for themselves. Every day, they endure violence from those closest to them. They cannot ask for help while remaining at home.

And they appeal:

When you see this sign, immediately call 112 and inform them that the person asked you for help in this way.

The video referenced by KPP in Lwówek Śląski can be viewed here: https://www.facebook.com/policja.lwowek/.