Screening Shall be used Safety sign - This sign is used to inform staff and the public that protective screens need to be used in this area while welding. This sign is often used to inform workers or visitors on specific sites what P.P.E. they require upon entering a Construction site, mine or even a workshop. This sign is used in conjunction with various other safety signs depending on what your requirements are, i.e - (ZM 20) - Overall safety sign