POSTERS, like signs, are a public noticeboard, although unlike signs, they are able to contain a more lengthy message to the public.
Posters work like signs or letters (see HELP SIGNS or HELP LETTERS) insofar as they are a means of conveying information to the general public. They differ from signs in that they can hold a lot more information - whole paragraphs - when READ and from letters in that they can be permanent additions to a location. They are fashioned using the standard city craftsmen and then written on using the WRITE command in precisely the same way as letters. It is then possible to take the poster to its proposed end-location and put it in place, for all to see, examine and read.