Short tutorial on how to use Cat-A-Lot on Wikimedia Commons

Wikimedia Commons is the media database of the Wikimedia projects. It is structures using categories, I've blogged about how categories work on 'Commons before. Yesterday Leon asked me if I knew a tool that would easily categorize a batch of images. Cat-A-Lot is a usefull tool for this. I made a short screencast explaining how to use it: