## The Penguin Grid

Anybody know what the diagonal lines are used for?

Their intersections determine where the horizontal lines go.

Proportion.

You may find this post at The Ministry of Type interesting.

So they really have no practical use for a person using this grid to lay out typography?

And what's with this point, what it is it based on?

I think the rectangle is a golden one, and these drawings are how to get what are supposedly--and maybe actually are--good proportions. For more of this stuff read Bringhurst's Elements of Typographic Style, or you can look at Tschichold's stuff on it. There is a long tradition of efforts like this. And those Penguin books were actually well designed. Tschichold and Schmoller were famous for lifting the game of book design in England after the second world war. However, this design was a bit later. Some of its story is here.

Ryan,
Take the upper right corner and make it perpendicular to the diagonal going from upper left to bottom right, that’s it!

So they really have no practical use for a person using this grid to lay out typography?

The grid was put to use designing some of the most iconic paperback covers of the twentieth century.

Perhaps these will help:

http://thebookdesignblog.com/book-design-articles/history-marber-grid

http://www.eyemagazine.com/feature/article/penguin-crime-text-in-full

@Ryan Maelhorn:
And what's with this point, what it is it based on?

Well, note that there is a diagonal from the upper left corner to the lower right corner of the page.

Then, a line going from the upper right corner crosses that main diagonal at a 90 degree angle to indicate that point.

That means that that point marks where you could draw a horizontal line to create a rectangle, made from the top of the page above the line, which has the same proportions as the page as a whole - because its diagonal makes the same angle, except rotated by 90 degrees, as the diagonal of the whole page.

This rectangle is then the basis on which the three horizontal lines you do see drawn are constructed.

First, the point where the rotated shrunk page diagonal crosses the main diagonal defines the bottom-most of those three lines.

Then, a diagonal is made for the left half of the rotated page image, and where that crosses the main diagonal defines the second line.

Finally, the bottom-most of the three lines is used to define a new thinner rectangle; where its diagonal crosses the main diagonal indicates where the top line is to be drawn.

Ah: this might help:

http://ministryoftype.co.uk/words/article/constructing_the_grid/

Why isn't there another instance of that point on the other side of the page? (mirror image)

One isn't necessary for the purpose of constructing the lines.

It should be noted, though, that you are right in being suspicious of this construction. It doesn't really embody some fundamental aesthetic principles. If the aspect ratio of the page were different, following the same steps would create a radically different, and thus presumably not necessarily attractive, layout. (And I presume that the existing aspect ratio is not exactly the golden ratio, even if it approximates it.)

So it is just that starting from the page as it is, following these particular steps happens to put the horizontal divisions in places that could have easily just been specified as numerical fractions of the page height.

I've used the diagonal lines in the past to inform the placement of photos in editorial, or when illustrating, so that the images adhere to the proportions of the page. I've included some examples above, based on grids derived from root rectangles.