I have a bitty, bitty classroom with many dry erase marker boards but no bulletin boards... a small problem. So I took this old frame, measuring about 30 inches square and made a faux French memory board.
Using craft twine [which may upset allergies, so cotton might be a better material] I started in one corner and proceeded to weave through the staples which had been left in from the previous art installation. I first created horizontal [or vertical, depending how you looked at it] rows, then moved on to the opposite direction. This is where the weaving, the over under over under really came in that you can see in the picture above. It creates a little tension in the strings, keeps them from flying everywhere when you try to clip something to them, and keeps the frame pulled together.
when I finished the project, I made sure that the two loose ends met so that I could tie them in a square knot. I also used a square knot any other time I ran out of twine and had to join two other pieces. The twine isn't very stretchy, so I don't have to worry about it loosing it's shape through the school year, unlike yarn, which is more elastic and would begin to sag unless pulled very tightly.
If the frame looks slightly off square, you're right; it isn't perfectly, square, and it top it off, the staples weren't at perfect square intervals either, adding to the tipsy effect.
The frame was $3 at a resale store, the twine was marked down at a craft store to $1, and the most expensive investment were the tiny clothespins at $3.50 for the bag of 20 [never again].