Here are some helpful tips to get your inserts fitted perfectly. Once your sleeve is carefully placed under the string/elastic of your outer notebook jacket, place your first insert on the string/elastic on top of the sleeve. After, place insert 2 on top of insert 1, only adding the front cover into the sleeve. Then on the back of insert 1, add insert 3, adding only the back cover into the sleeve. Now you have 3 inserts in your notebook jacket only occupying 1 string/elastic. You can stop there or keep adding like this: Close the sleeve with the 3 notebooks inside and place a 4th insert, cover only, into the front pocket of the sleeve. Then repeat with insert 5, inserting the front cover into the back pocket of the sleeve. Now , you have 5 inserts on 1 string.

If you are using a larger notebook as the first insert, slowly and carefully fold the front covers down, inserting them into the interior sleeve pockets, like wings. Carefully stretching the vinyl closed. You may need to mold the cover to your book by adding a heavy object on top for 24 hours or (my preferred way) using a heat tool or a hair dryer to apply a bit of heat to the spine of the notebook. This helps the vinyl mold to the book, making the cover fit like a glove. 

The opposite does NOT apply. You can not then shrink a vinyl cover with cold temperatures to smaller than the original size. They may return close to their pre stretched size but they will never shrink smaller than their original size. Our vinyl is INTENTIONALLY a thin and malleable material and thus able to stretch to fit up to a 1 inch spine, like archer and olive, paper minty and other hard bound books. There is also a full video on my IG stories, showing the heat stretching process HERE