Natural fiber sweaters, such as those made from sheep's wool or alpaca fur, stretch much more readily than artificial fiber sweaters, such as polyester. The natural fibers loosen when wet, and therefore will stretch to accommodate the wearer.

Soak the sweater in water, or wash according to the product label instructions. Remove the sweater from the water, and after gently wringing out the excess water, spread out the sweater on a dry towel.

Roll the sweater and the towel together, like a piece of sushi. By rolling the sweater and towel together, the dry towel will extract much of the moisture from the sweater without damaging the sweater.

Unroll the sweater, and lay it out on top of the blocking board. Gently smooth out all the wrinkles so the sweater is laying completely flat on the blocking board. Position the sleeves at 45 degrees to the body of the sweater.

Gently stretch the sweater, and using the stick pins, pin the garment to the blocking board stretched to a larger profile than if the sweater were laying relaxed on the board. Use enough pins so that the outline of the garment is stretched evenly across the board, without deforming the shape of the sweater. Pull the sweater into larger dimensions vertically and horizontally.

Allow the garment to dry naturally in the larger size. The fibers will relax as the sweater drys, and it will stay in the stretched size.