A lug is a protrusion on the case of a watch to attach a strap or bracelet. Nearly all watches feature a bar (usually sprung) between lugs to attach the strap or bracelet, but some have “hidden” lugs and are said to be “lugless”.
Lugs are one of the primary stylistic features on a watch. The location, size, and shape of the lugs does a great deal to define the overall style of the watch, from the earliest soldered wire lugs to various stylized lugs in the 1940's and 1950's to the integrated lugs in the tonneau cases popular in the 1960's and 1970's.
Typical lug styles include the following
Another, particularly secure method of attachment are screwed lugs. However, it is a matter of opinion whether this is a better solution, as this method is more expensive and more complex to install, and tends to be stylistically disadvantageous on elegant watches. In individual cases (diver's watchs, expedition watches, officer's watches or in other cases, for example for historical watch genres), however, it may be indicated.