You decided to tell someone to make a book for you. You need to tell him what shape you would like the book to have. But since you want it to be quadrilateral, you need to go there and make sure that the person is doing it correctly. So that they don't give you the book with a shape of a triangle, then you would have problem to add it on your shelf because it wouldn't look interesting.
Note: A quadrilateral is defined as a polygon (a closed shape) with 4 sides,
so any shape/object with four sides can be considered a quadrilateral.
