Use a box knife to remove the old rush by cutting along the chair side rails all around the chair frame. Do not cut into the wood of the rails. As you remove the rushing, notice the tacks on the inside of the frame and use this as your starting point. Use a tack puller to remove the old tacks.
Begin rushing on your left and continue working left to right, keeping your work tight. Start by tacking the rush near the hole where the old rush was placed, and wrap the rush over the front rail. Next, bring the rush under the front rail and over the rush on your left.
Place the rush under the right chair rail, and then over the side rail. Next, run the rush under the front rail and back to the back rail. Place the rush under, and then over the back side rail. Bring the rush under the seat over to the left side rail, working your way from back to front.
Position the cardboard triangles under the rush, stacking them on top of each other until the gap between the cardboard and the rush is tight. Continue weaving in that pattern, using a screwdriver to tap the rush and keep it tight. More room will appear from the top to the bottom than from left to right at this point. Use a “figure eight” weave from front to back and tack the rush under the seat at the back rail when you are finished.