What does it mean to post a banner in front of the door during the epidemic?

In order to fight the epidemic, putting a seal on the door

It means that a person is isolated at home, as long as the seal is broken. This means that people who are quarantined at home are not really quarantined at home. At this time, if they are discovered by anti-epidemic personnel, they will be taken away directly for centralized quarantine. To combat the epidemic, put a seal on the door. It is a reasonable approach.