Greetings. I'm relatively new to Python-based development of Zope products. I've got two classes in my product; let's call them Container and Thing. I want to have Container addable to any old folder in the ZMI; that's no problem, I just register it in my product's __init__.py file. I want Container to allow instances of Thing to be added to it, and nothing else; that's also no problem, using all_meta_types. However, I want Thing to be addable to Container, but not to any other ObjectManager-based object. I can't figure that one out. I assumed I could do it by having an entry for Thing in Container's all_meta_types property, and by *not* registering it in __init__.py. Unfortunately, that fails. If I click on the "Add Thing" button in the ZMI when viewing the content of a Container, I get Cannot locate object at http://localhost:8080/kb0/manage_addProduct/ [ignore line break] MyProduct/manage_addThingForm If I register Thing in __init__.py, then the Add Thing button works perfectly, but I can add a Thing to any folder in the ZMI. It looks like the registration process is necessary to get manage_addThingForm added to whatever registry of constructors manage_addProduct['MyProduct'] accesses. Is there a way around this? I'd think what I'm trying to do is pretty standard, but I can't find anything enlightening. Thanks, ..Ian