The raglan sleeve is a popular choice for casual knitting projects. Raglan shaping is usually worked from the top down and involves a long, slanted seam running from the neck to the underarm.
Raglans have no shoulder seam; the expanding sleeve cap becomes the shoulder of the garment. The shaping of the sleeve must match the front and back shaping so that all the pieces fit together properly.
Because raglan shaping produces such a clear line on the front (and back, of course) of a garment, the increases used to add width are often decorative. Yarn overs may be used on a women's garment, or a cable or another decorative feature may be worked along the raglan line to bring more emphasis to the shaping.
The raglan style is a popular choice for sewn garments, particularly athletic clothing and other casual styles.
The style is named for Fitzroy Somerset, also known as Lord Raglan, the commander-in-chief of forces during the Crimean War (another commander lent his title to the cardigan). Raglan lost his right arm in the Battle of Waterloo and some have speculated that the raglan style was developed because the sleeve fit better on his armless side than a traditional shoulder and sleeve.
Richard Rutt's A History of Hand Knitting reports that the term raglan was first found in the dictionary in 1864, nearly a decade after Lord Raglan's death. It originally referred to sewn garments; raglan sleeves in knit garments were first seen around 1912, Rutt writes.
The Men's Beaded Rib Sweater uses raglan shaping in a pieced garment, though it's also common to see garments with raglan shaping worked in one piece from the top down, increasing from the neckline then putting the sleeve stitches on hold while the body is worked.