Like other handicrafts, knitters can create a sampler of knitting stitches to display their skills or merely to document a stitch. Many knitters did this in the 19th century to document and preserve stitches they had learned or obtained from other knitters.
Here is an example of a sampler at the Powerhouse Museum:
Knitting sampler, 1876
Franklin Habit wrote a great article at Knitty.com and offers his version of Miss Lambert's Lace Sampler.
The lace patterns used for this sampler were taken from My Knitting Book (1843) by Frances Lambert available on Google Books.
It makes a nice scarf!