What feature do drums have at the top?

Drums in work zone safety are designed with closed tops to minimize the risk of debris falling into them and to prevent unauthorized access. This design helps maintain the integrity of the drums, ensuring that any materials or messages intended to be displayed remain protected from environmental factors and possible tampering. The closed tops also make the drums stackable and easier to transport, as they reduce the likelihood of spillage. This feature is crucial for maintaining safety standards in work zones, where visibility and proper marking are essential for guiding both drivers and pedestrians safely past construction areas.