How to Add a Preview Pane to Gmail

Four corners made The Bismarck (available in mahogany and blond) different from most other TV sets sold in 1956.
Pointing Zenith's own Flash-Matic at these corners controlled The Bismarck remotely and without wires or cords. One could change channels, mute and turn the TV off or on.
In Gmail, to add the four corners of a preview pane, control your pointing device thus:
›› Like to read your email and have an inbox overview, too? Here's how to add a preview pane to Gmail and read messages in it, choosing a widescreen layout or a traditional one as you prefer.