How did wards in Roman locks stop the wrong key from turning?

The Romans invented wards, which are internal projections positioned around the keyhole that act as physical obstacles to unauthorized access.12

These projections prevent a key from rotating unless its flat face, known as the bit, contains precisely cut slots that align with the specific arrangement of the wards. If a key lacks the correct corresponding slots, it will strike the projections and be unable to turn, thereby keeping the bolt secured. While this system was the primary method of security for centuries, warded locks were historically vulnerable to picking, as instruments could be fashioned to bypass the internal projections regardless of their complexity.12