What does wipe style 'Box' do in the color page?

What does the wipe style ‘Box’ do?
On the color page, when choosing image wipe and wipe style, this icon is present.

Screen Shot 2016-11-30 at 12.57.13.png (11.11 KiB) Viewed 1083 times

The icon looks like a small PiP, but I can’t seem to get it to do anything when using a reference still.

The manual doesn’t specify what it does and how to use it.

[edited for clarity]

Don't know but you might want to edit the thread title so people don't think you're talking about the edit page transition while they are browsing the forum, they probably won't click on it thinking it's just a silly question

[Dmitry Kitsov BMD]

At this time this wipe style is only active when using an offline reference clip. This is helpful in alignment of scale and position.

At this time this wipe style is only active when using an offline reference clip. This is helpful in alignment of scale and position.

Thanks, good to know