Prohibition Signs specify when a general instruction or action must be adhered to. When you need to tell people that they can’t do something, you’ll need a Prohibition Sign. These safety signs feature the universally recognisable red circle or annulus with a diagonal line through it. Keep people from entering private property with a NO ENTRY sign or signal that people aren’t allowed to smoke in an area with a NO SMOKING sign. Sign wording is in black lettering on a white background. Sign layout must comply to AS 1319 regulations.