Dwight Sipler wrote:

The strips of aluminum can will have sharp edges, so you might want to
bend them over to avoid hazards to small children and pets.

I think cutting up a bleach jug and using a permanent marker might be a better
idea. No sharp edges and the plastic lasts a long time. Could be a use for
old floppies too. Thread a wire or string through the hole and write on the
floppy with a marker.