## Thursday, 25 February 2016

### The Haylock Bookmark

When I am in the middle of reading a book I need a bookmark that not only helps me to find the page I am on, but also exactly where on the page I should start to continue my reading! I offer readers my design for an effective bookmark for this purpose and a simple example of mathematics applied to another area of the curriculum!

First measure the height of the page of the book (h mm) and the height of the smaller of the top and bottom margins for the text on the page (x mm). Cut a rectangular piece of firm card so that it has a length that is equal to h/2 + x. The width can be whatever you wish, say, about a third of the width of the book.

For example, for a standard paperback novel I find that h = 198 and x = 19. So we need the bookmark to be 99 + 19 = 118 mm long.

Then on one side of the card draw a double-headed arrow x mm from the top (i.e. 19 mm for our standard paperback). The diagram shows a bookmark made for this standard paperback.
That's it! Now, when you have finished your reading session place the bookmark in the fold of the book on the opposite page to the one you are on, with the arrow showing and pointing to your place on the page. This might involve rotating the bookmark, of course, depending whether you are on the top half or the bottom half of the page. Then just close the book. When you open it next time just make sure you have the side of the card with the arrow visible, and remember that the arrow tells you where on the opposite page you should start reading again!

With this system any starting point on either the even-numbered page (verso) or the odd-numbered page (recto) can be marked, without the bookmark sticking out of the closed book (which I don't like).

The diagrams below show the bookmark placed inside the book to mark (a) a point half-way down the left-hand page; and (b) a point near the bottom of the right-hand page.

(a)

(b)

Well, it works for me. And it is a good application of simple measurement and spatial reasoning!