Bobby pin

A bobby pin (also known as a kirby grip or hair grip in the United Kingdom) is a type of hairpin, usually of metal or plastic, used in coiffure to hold hair in place. It is a small double-pronged hair pin or clip that slides into hair with the prongs open and then the flexible prongs close over the hair to hold it in place. They are typically plain and unobtrusively colored, but some are elaborately decorated or jeweled. Bobby pins became popular in the 1920s to hold the new bobbed hairstyles.

Uses

The main use of a bobby pin is to hold hair in place. In addition to bobbed hair, bobby pins are often used in up-dos, buns, and other hair styles where a sleek look is desired. To use a bobby pin in hair hold the hair in the desired position and push the bobby pin (straight side up) into place.

Bobby pins can also be used to hold head coverings such as headbands, bandannas, and yarmulkes in place.

They can be used as decorative elements in hair.

Attributes such as the clipping action or the having a readily available thin, flat piece of metal mean the bobby pin can be used in other ways as well:

Spiral

In mathematics, a spiral is a curve which emanates from a central point, getting progressively farther away as it revolves around the point.

Spirals and helices

Two major definitions of "spiral" in a respected American dictionary are:

Definition a describes a planar curve, that extends in both of the perpendicular directions within its plane; the groove on one side of a record closely approximates a plane spiral (and it is by the finite width and depth of the groove, but not by the wider spacing between than within tracks, that it falls short of being a perfect example); note that successive loops differ in diameter. In another example, the "center lines" of the arms of a spiral galaxy trace logarithmic spirals.

Definition b includes two kinds of 3-dimensional relatives of spirals: