As I was walking past a housekeeping storage room at a hotel, I couldn't help but notice that the storage locations were marked on the shelves (click on the photo for a larger view).
As you can see in the picture, they labeled not only “what” goes where, but “how many”, which is a key point for 5S-ing stock shelves and locations.
One thing they didn't do is mark boundaries of where those towels are supposed to go (with tape lines, etc.). But still, it's better than many factories I've seen that just mark “what” while ignoring the “how many.” 
If you’re working to build a culture where people feel safe to speak up, solve problems, and improve every day, I’d be glad to help. Let’s talk about how to strengthen Psychological Safety and Continuous Improvement in your organization.
In addition to boundary lines, vertical “Quantity Lines”, in red/green placed behind the towel stacks would show qualities without having to count towels.