If you’re using this as a headline/hook, it’s intentionally vague—the “tool” isn’t identifiable from the sentence alone.
A stronger version could be:
Mystery Tool Hook
Millions of people use this tool every day—but most have no idea about the clever feature hiding in plain sight.
If you tell me which tool you mean (kitchen tool, household item, phone feature, gardening tool, etc.), I can make the hook specific and compelling.
