Use your yardstick to mark the edges of the grid on the top, bottom, and sides of your paper. Then, line up the marks on the top and bottom, and use the yardstick and pencil to draw a faint ...

1, 2, 3, and imagine highlighting the whole row marked three. Where the letter column and number row meet, is square C3, which is where you’re standing. That’s called a grid reference.