This is designed to accompany the line assignment. It really tests the student's knowledge and understanding of the element we call 'line.' I usually have my students design a grid on a sheet of 14" x 17" Bristol board. It needs to be heavy card stock like Bristol Board or Poster board because of it durability and how the cards feel once they are cut out of the sheet.
This is an excellent opportunity to teach some basic drafting skills. I have a portable drafting board with a slide rule attached. I use this and a large triangle to show my students how 9 cards can fit on one sheet of 14" x 17" Bristol board with an inch border around the outside and a little over 1/2" between each column.
I usually have to demonstrate this more than once but they actually enjoy 'mapping' out their own cards.
For grading convenience, they turn in the entire sheet of cards and we cut them out after I grade the project and return their work.
I have displayed these cards in the hall way with a regular deck of cards as the border around their work and it looks great!