In Western handwriting, the base line, the x-height

X-height

In typography, the x-height or corpus size refers to the distance between the baseline and the mean line in a typeface. Typically, this is the height of the letter x in the font , as well as the u, v, w, and z...

 or corpus size, the height of the ascenders and the bottom line of the descender

Descender

In typography, a descender is the portion of a letter that extends below the baseline of a font. The line that descenders reach down to is known as the beard line....

s make up four horizontal (virtual) lines which represent the lineation of handwriting. In many teaching methods of writing at primary school, these guidelines are actually present on paper to aid the child in producing well-formed characters of the proper size. In adulthood the lineation remains, virtually, and can be used in handwriting recognition

Handwriting recognition

Handwriting recognition is the ability of a computer to receive and interpret intelligible handwritten input from sources such as paper documents, photographs, touch-screens and other devices. The image of the written text may be sensed "off line" from a piece of paper by optical scanning or...

 by performing an analysis of the horizontal density of minima and maxima of the writing trace. The density at the base line of handwriting will be highest, followed by the density of the corpus size. As ascenders and descender

Descender

In typography, a descender is the portion of a letter that extends below the baseline of a font. The line that descenders reach down to is known as the beard line....

s occur only infrequently, their densities will be low, especially if a single word is considered.