[Zope] Change Ownership

Hi, Can someone explain for a dummy like me how I'm supposed to change the owner of an object? I always assumed it'd be on the Ownership tab, but while that shows you who the owner of an object is, it doesn't let you change it. Basically, a the object is owned by a summer student who has since left, my only option now is to re-create a user object for them with a garbled password, which is majorly sucky! cheers, Chris