After resting and tugging the canvas, pin the corners of the canvas to the blocking board. Pull and stretch the sides of the canvas and pin to the boards along the grid lines using the marked grid lines as your guide to square the canvas. Place enough t-pins to hold the canvas securely in place and place them as close to the edges of the stitching as possible. Space the pins about 1-inch apart.
WARNING: Do not simply "stretch" the piece! Re-shape the piecce by using stretching in some areas, and by easing the "give" in other areas. Otherwise your piece may not stay in its proper shape.
Allow the canvas to dry for several days before removing the t-pins.
Note: If simply blocking the piece, pin it face-up on your blocking board. However, if you plan to apply stiffener or sizing to stiffen the piece, place it face down on the blocking board, and apply the sizing to the back of the piece after it has dried. Keep the piece pinned to the blocking board until the sizing or stiffener dries as well.
If your canvas was severely warped, you may need to repeat the process an additional time. You may also give it a shot of hot steam with your iron and allow it to dry thoroughly for several days if your canvas is particularly stubborn.
TIP: Never, ever iron or press your finished canvas! Ironing and pressing flattens the fibers and ruins the texture of your beautiful needlepoint creation, especially on textured or decorative stitches.