For many men, finding a button-front dress shirt that fits correctly can be difficult. If a shirt fits at the collar, the sleeves may not be the correct length, the shoulders may be too wide, or the body too full. “Standard” sizing for men’s apparel has some of the same problems as women’s sizing: The proportions are often ideal for only a small portion of the population.

Although it’s possible to hide some fit problems under a suit jacket, casual office and leisure settings rarely call for jackets these days. To look neat, pulled together, and modern, it’s worthwhile to assess whether your shirts have enough ease where it’s needed, but not too much, and that the body and sleeve lengths suit your build.

Many brands sell dress shirts with descriptive labels such as “regular” or “traditional” fit, “slim fit,” and “athletic fit.” (Not all brands offer each of these cuts.) The regular fit is usually a fuller cut with pleats in the back below the yoke. A traditional Brooks Brothers shirt is cut this way. Slim-fit shirts typically do not have these pleats. They usually have side-back darts to create a closer silhouette at the back waist. John Varvatos brand shirts are a good example of this kind of fit. The athletic fit has a fuller cut than the regular, with wider sleeves to accommodate muscular arms. Even with these options, a well-fitting shirt off the rack can prove to be elusive. But, with a little altering, most fit issues can be resolved by someone with intermediate sewing skills.

In this installment of a two-part article, I’ll show you how to adjust the fit of a shirt’s back. This area often includes excess ease as well as length. Today’s styles are more fitted than…