From the creator's web site:
An indexing mechanism or intermittent drive is a mechanism that turns a wheel or shaft a small amount then stops for a set amount of time the turns again repeating this process over and over as the drive handle is turned.
Indexers are used for all sorts of things including digital displays when a sequential number can be displayed or in machines used to cut gear teeth.
This paper indexer has a twenty four tooth drive wheel. It takes twenty four full turns of the handle for the geared wheel to make one full turn. Download and make this model to find out first hand just how an indexer works. Use it as an exercise in pure mechanism or as the starting point for your own designs.
You can download and make this paper indexing mechanism. It will cost you £2.50 (about $3.90). Well worth it, I would say.