Because the form of a wedding invitation is usually traditional -- an engraved, folded sheet inside a double envelope -- the smallest detail can set yours apart.

Format and Size
At its most formal, the invitation is a stiff letter sheet, folded once, with a piece of tissue protecting the type. It is placed within an unsealed envelope bearing just the name of the guest, and is then placed in an outer envelope with the full address. In the days of varnish-based inks, the tissue prevented the type from ghosting (smudging); tissue-lined envelopes can serve the same purpose. The inner envelope protected the invitation from grubby hands. Both elements live on to ensure the receipt of a pristine invitation.

The two most frequently used invitation sizes are 4 1/2 by 6 1/4 inches (classic) and 5 1/2 by 7 1/2 inches (embassy). The form can be a single card, a folded sheet with the printing on the outside, or a double-folded sheet with the printing on the inside. (For the traditional style, a single-folded embassy is folded again to fit into a smaller envelope.) Each stationer will have its own selection; the bride and groom can simply pick the format that suits the paper and printing style they have chosen.

Paper
An exquisite invitation should also serve as a memento. Use a paper that won't disintegrate over time: 100 percent rag, made of cotton or linen, is best. Papers made with wood pulp, which is highly acidic, can discolor. An invitation can be personalized by using handmade paper, which tends to have interesting textures and colors. Art-supply stores often carry a wide selection.

Weight
Stationery is usually measured in bond weight. A good letter sheet is made of 32- or 40-pound bond. You may also come across offset weight: 100-pound offset is roughly equal to 40-pound bond. Heavy cards should be made of three-ply stock.