What are the most effective non-medical masks for preventing community transmission of COVID-19, and should they be required for all of society?

We identified 11 documents that provide highly relevant evidence to answer the question, which includes: 1)   one highly relevant systematic review; 2)   three highly relevant rapid reviews; and 3)   seven guidelines that were developed using some type of evidence synthesis and/or expert opinion and by seven groups, namely two groups of multi-country teams of researchers (one publishing in BMJ and the other in The Lancet Respiratory Medicine), Centers for Disease Control and Prevention (U.S.), Emergency Care Research Institute (U.S.), European Centre for Disease Prevention and Control, Joanna Briggs Institute, and the World Health Organization.