Sending secret messages without leaving a trace? We did it better than intelligence agencies because we had these delightful magnetic boards. Often coupled with stencils and stamps, the plastic board came with a plastic pencil that you could use to write on that board. Once you have finished writing and your friend has read the message, simple lift the board and Abracadabra, It’s gone! No possible trace of what you wrote, no paper to dispose, no record to destroy. If you were in one of those schools that allowed you to bring such toys to school, you might have communicated so many secret messages across the classroom, removing all evidence before the teacher could realize what was even written. Simpler times, right?