Clou

Clou is a French noun meaning “nail,” the metal fastener used to join materials such as wood, metal, or plastic. The word derives from the Old French *cloue* and ultimately from the Latin *clavus*, also the source of the English term “clavicle.” In construction and carpentry, a clou is driven into a workpiece with a hammer or nail gun to create a permanent or temporary joint, and it comes in a variety of sizes, lengths, and head types to suit different applications. Specialized clous, such as roofing clous, upholstery clous, and finish clous, feature distinct shapes and finishes that reduce corrosion or improve aesthetic appeal.

Beyond its literal sense, clou is employed metaphorically in French to denote the “crux,” “key point,” or “essential element” of an argument or situation, as in the expression “le clou du spectacle” (the highlight of the show). This figurative use reflects the notion of a nail as a pivotal fixing point. In other contexts, the term appears in idioms such as “être cloué au lit” (to be bedridden) and “clouer quelqu’un” (to defeat or immobilize someone). The word also functions as a verb, *clouer*, meaning “to nail.” Although primarily French, the concept of a clou is universal in building practices worldwide, where various languages have their own terms for the essential fastener.