Solid lines are continuous lines that do not have any breaks or interruptions. They are often used in various contexts, such as in geometry to represent boundaries or in art to create clear shapes and forms. Solid lines can also indicate a strong connection or relationship between elements in a diagram or illustration. In traffic regulations, solid lines are used to convey important information to drivers. For example, a solid line on the road typically indicates that changing lanes is not allowed. This helps maintain safety and order on the roads by clearly marking where vehicles should and should not travel.