'Nuther Good Question
Posted because, uh … I don’t know, and absolutely should:
When trade paperbacks have folded covers to immitate the slip cover of a hardback, what is that called? Overleaf? I want to design a book with these cover elements, and want to describe it properly to the printer.
I’ve only done one — Florida’s Birds — and just referred to it as a “flapped paperback.” (No flapping bird book comments, please…;)
Checked a couple of sources but didn’t see it specifically named. Can anybody help us out? Thanks.

Comments:
That’s a French fold, no? Unless I’m not understanding what you’re describing.
Yup, I’ve heard them referred to as either French flaps or folds.
Yes, either French fold or French flaps.
Cool. Thank you!
No!
A French fold is a page bound in at both ends with the fold at the fore edge — sometimes perforated — like a secret page.
Not sure of the correct term but what your suggesting sounds like something similar to a Gate fold.
Post the answer back if you get one!
The cover flaps described by Giles in his post are definately called “french flaps” where I work, near Vancouver, Canada. Have used them many times, but I’ve never heard the term “french fold”. Maybe they’re french flaps when used to extend the cover, and a french fold when used on interior pages?
Ok, I’ve dug a little deeper. James is correct. French fold is incorrect. However, French flap is the correct term. I found this definition: A book with French flaps indicates a trade paperback with long covers which are folded inwards.
I’m nearly a month late on this. But I do have some notes to add.
FRENCH FLAPS is the current term to describe a paperbound book with flaps, in emulation of a book jacket.
FRENCH FOLD is an old-time job printing term. Fancy cards & invitations are often done French Fold. A standard greeting card has 4 printed surfaces. If you print this French Fold, you print all 4 surfaces on the same side of the sheet. You then fold it twice so you can avoid a second press run, and also so the thing can look and feel more substantial. Take my word on this. I was a job printer for decades, and made a lot of loot doing hifalutin’ French Fold wedding and party invitations.
WHAT IS NOT FRENCH FOLD is the binding described above in which the foredge of a book consists of folds, and the sewing is done through the ends of the sheets. This describes an ORIENTAL style of binding, still seen in some work from Japan and China. Take my word on this, too. In addition to job printing I printed limited editions, and this is a trick often used to bulk out the book and also to use a nice exposed-cord binding. And thus to charge more.
In BOTH French & Oriental bindings the “inside” of the sheet is blank.
powers
Interesting. No matter how long it took, thank you for the update.