Fill the full page with accurate measurement, another dummies way

Do u know how to fill the whole page ? or create rectangle same as the page with accurate measurement ?

something like this

1. you can make rectangle and go to " size " dialog box on transform (accurate ???)

2. or.................YOU CAN CLICK RECTANGLE IN TOOL BOX...TWICE !!

I promise you the second step is the best & simple way..................and accurate ;)