[Question] What are these section markers/tabs called?

I'm specifically talking about the markers on the top/side edge of the page that change with the section of the book (they become highlighted in some fashion). They let you quickly see what section you're in while you flip through the book.

Example I quickly threw together: http://ift.tt/1Nd5VMQ

Is there a name for them?

Great design resource

100 Things Every Designer Needs to Know About People (Voices That Matter) Submitted October 04, 2015 at 02:07AM by rootb33r http://ift.tt/1RnPADP