Wrap burlap around the boxwood in a single layer. One person holds the end of the burlap in place while another wraps. Arrange the branches inside so they bend upward, as downward-bending branches are more likely to break.
Wind a length of twine around the boxwood near the bottom of the burlap-covered area. Tie the twine together to hold it in place. Continue wrapping the twine until you reach the top of the burlap, then tie the end of the twine. Wrap the boxwood tight enough so the burlap stays in place, but not so tightly that the twine forces the branches out of shape.
Remove the burlap in late winter after most danger of hard frost is past and before the boxwood begins putting on new growth. Overheating occurs if the burlap is left on the shrubs for too long after temperatures begin to warm.