close up view of a black dirty chalkboard without a wooden frame.

advertisement advertising background black blackboard blank board brief chalk chalkboard class classroom clean close closeup communication concept copy creative cryon design dirty draw drawing dusty education element empty filled formula frame full further gradient great grunge grungy idea layers layout learning lesson meeting menu message natural old original out pattern plate primitive record rubbed school slate smooth space style surface teach teaching template texture textured unclean view white without wood wooden write