This is a little ditty for librarians everywhere...
If you use a shelf marker system in your library, we may share the same frustrations! (Especially when explaining how and why we use them to the smallest kids, who don't think twice about organization!)
Here's a song I found that has helped students understand what a shelf marker is for. Hope it helps you, too!
(Sung to the tune of Hokey Pokey)
You put your shelf marker in, you pull the book out.
You leave the marker in -- now, will you check it out?
You read a couple pages to see what it's about:
Put it back if you're in doubt!
Of course, a demonstration of what you're singing is the best part of the song. I've caught a couple kindergarten students singing it to themselves now, so it must be working!