Classrooms operate more smoothly when procedures are in place. In most classrooms students raise their hands to get the teacher's attention. This is an excellent procedure, but It would be better if teachers know the reason that students' hands are being raised.
I incorporated a finger raising system in my classroom. If a student raises one finger, then I know that he/she needs help with an assignment or task, two fingers let me know that the student needs to sharpen a pencil, and so on.
The posters that you are about to purchase are for you to place around your classroom to remind students of these procedures.