catering companies that deliver to key enterprises belong to the employees of the supplier-guaranteed enterprises, while ordinary catering personnel are not. Belonging to the security supply unit can go out of the community gate. According to the relevant information of the inquiry, the classification standard of the guaranteed supply enterprises is recommended by the street or by the county market supervision bureau, industry associations and other relevant units. Or apply voluntarily and have the ability to guarantee the supply. Or the isolation point decided by the county government, it will be automatically converted into a guarantee unit. Or the medical staff of the shelter hospital requisitioned the hotel catering unit and automatically turned it into a white list guarantee unit.