Geometric designs are not straightforward and take a bit of thought to prepare but after creating them they can be repeatedly used.
In this illustration we will create a Gingham pattern.
2. Select this rectangle and from the Object menu choose Transform and Move. In the Horizontal box put 2mm and Vertical 0mm. The Distance will automatically change to 2mm. Now press the Copy button. This will duplicate another box exactly the same size but 2mm offset.
3. Create 4 squares horizontally and 2 squares deep by using the Move command you know they are exactly 2mm apart.
4. Remove the stroke from all boxes. Color boxes 1,3,6 and 8 with 50% black.
5. Fill boxes 5 and 7 with 80% black and boxes 2 and 4 are 0% black. Your result will look as the example below.
6. Choose the Selection tool and drag the eight rectangles into the Swatches palette.