That didn’t work. It messed up content on the Portfolio pages. It didn’t just take away the sidebar on a single Portfolio post page. : /
I use those attributes on other pages, and I’m familiar with them, however the “portfolio entry” pages don’t give that option, like the regular pages do. The type of post I send as a screenshot doesn’t show up under pages, only under portfolio entries and those don’t list attributes on the side like pages do.
Here are a couple of screenshots of the backend of a portfolio entry: