Remove(hide) left hand bar bookmark,reading list,history

For iPadOS 15.x, the Safari Sidebar is now closed with the Sidebar button at top-left of the screen:

For iPadOS 13/14, tap the blue-highlighted Book icon:

On iPadOS 15 you tap the Sidebar icon - the top left icon to the left of the history arrow keys. I’m not sure if that icon is in the same place on iOS 9, though.