The correct spelling of the phrase "plumb level" is often questioned due to its pronunciation. Phonetically, "plumb" is pronounced as /plʌm/, which rhymes with "bum" or "thumb". Meanwhile, "level" is pronounced as /ˈlev(ə)l/, with the first syllable rhyming with "rev" or "heave". The two words are often used together to refer to a vertical measurement tool or a perfectly perpendicular surface. Despite the slight confusion about its spelling and pronunciation, "plumb level" remains widely used in the construction and engineering industries.
Plumb level, also referred to as "plumb and level," is a term commonly used in construction, carpentry, and related fields to indicate an object's precise alignment with respect to verticality (plumb) and horizontality (level). It is a measure of the object's straightness in relation to the force of gravity.
The term "plumb" pertains to the vertical alignment or perpendicularity of an object relative to the Earth's gravitational pull. When an object is described as "plumb," it means that it is perfectly vertical, with a line or surface parallel to the force of gravity acting on it, ensuring that it is straight up and down. This is typically achieved through the use of a plumb bob, a weight suspended from a string that aligns with the vertical axis.
On the other hand, "level" denotes the horizontal alignment or parallelism of an object with respect to the Earth's surface. When something is said to be "level," it means that it is completely flat and undistorted. This can be determined using a level tool, such as a carpenter's level or a spirit level, which incorporates a bubble chamber within a transparent tube. The bubble indicates whether the object is at a perfect, even horizontal position by centering within the chamber.
Combining "plumb" and "level," the term "plumb level" signifies an object or surface that is accurately aligned both vertically and horizontally, adhering precisely to the pull of gravity and maintaining a flat, undistorted appearance. Achieving a plumb level condition is essential for the proper installation, construction, or alignment of various structures, fixtures, or components in order to ensure stability, functionality, and aesthetic appeal.
The etymology of the word "plumb level" can be traced back to the Middle English period.
"Plumb" comes from the Old French word "plombe", meaning "lead", which was related to the Latin word "plumbum" with the same meaning. In ancient times, lead was commonly used to make weights for measuring purposes. The term "plumb" eventually came to represent the vertical or true perpendicular direction.
"Level", on the other hand, comes from the Middle English word "level", which derived from the Old English word "læfel". This word has connections to Old High German "libila" and Old Norse "leffl", both meaning "level" or "even".
Combining these origins, "plumb level" came to represent a tool or instrument used for making sure that something is both vertically "plumb" and horizontally "level".