Board Thread:Support Requests - Getting Technical/@comment-26424077-20160719203528/@comment-168424-20160726164933

A sandbox page is just any page where you can experiment that people should not expect to be an informational article. Many wikis have sandbox pages like Sandbox (which in this case redirects to Community Central:Sandbox). Putting your sanbox page at  is a common practice.

Many users make a sandbox page as a subpage of their user page like Special:MyPage/sandbox.