Part of Ireland's TNR Manual
How to Help Community Cats
Whether to use a poster to advertise your TNR project is something you'll need to decide on a case by case basis. If you're just neutering two or three cats, a poster is probably overkill, and not needed. Posters are most appropriate where you're Targeted Trapping and need help from local residents to identify all the cats in the neighbourhood.
Keep in mind that there are people out there who would harm the felines. You don't want to make things easy for them, or get their focus. So only use the poster in conjunction with a general publicity campaign in the area. And keep in mind you may get negative feedback alongside the positive.
You can download and adapt an example TNR Poster here (pdf).