Depending on the object, I think the only REAL way to animate appearing/disappearing is to use the Material Lab. You cannot set up a "Create" keyframe in Bryce, Ricky... And unfortunately, you cannot animate the "Hidden" attribute. Go into the rod's material, Rnollman, and "Copy" the mat you are GOING to use to the clipboard, using the tab right below the quick-preview window. Next, set the object to "Blend Transparency", and turn the transparency up to 100, no refraction necessary. If it's noon auto-keyframe, ADD a keyframe here. Your rod will be invsible. Then just advance to the correct key where you want that particular rod to reappear, add a key, and click "Paste" form the clipboard menu. Boom! Using this technique, you can also fade objects in and out as well...