If you search for "desk pad" on Amazon, Google images, etc. you'll see them. A large rectangle of paper, typically being held in a base at the corners, top and

If you search for "desk pad" on Amazon, Google images, etc. you'll see them. A large rectangle of paper, typically being held in a base at the corners, top and corners, etc., sometimes printed with a grid, calendar, etc. My father's desk featured one of these, used exactly as described.