Sliding glass changeable letter boards ensure that all displayed information will be clearly visible.The sliding, safety glass windows move back and forth easily using the low profile handle, and lock into place to secure and protect information. Key included. Complementing the felt changeable letter surface is a radius corner aluminum frame with a powder coated finish.To securely mount each board, a unique anti-theft locking system is provided. For indoor use. Black Felt Includes 318 white 3/4" (19mm) Helvetica style characters.   other letters available seperately