A changeable letter sign system including a plurality of panels, each bearing a letter, character or other suitable indicia and combinable on an overhead readerboard to display a message thereon, each of the panels having magnetically attractive material carried on the normally front face thereof, in complete contiguous arrangement with the peripheral inner and outer edges of the indicia on the panel, and including a tool having a magnet presenting a pair of feet for engagement with said magnetically attractive material to permit holding of the panels for placement on or removal from suitable retaining means on the wall of the readerboard.