For the cover, cut a long rectangle from heavyweight paper. Its length should be four times the width of the bound envelopes, plus the width of the spine of the bound envelopes; the width of the rectangle should equal the length of the envelopes plus 1/4 inch. Locate the center of the rectangle. Using a bone folder and a ruler as straightedge, score a crease to either side of the center, marking a band as wide as the spine. Fold inward along creases; press with bone folder; open again. From each crease, measure outward the width of an envelope plus 1/4 inch; score and fold inward along these creases.