The video shows stockinette stitch; however, this technique can be used to determine gauge for any stitch pattern.
Using a circular needle of the size called for in the pattern, knit across.
Carry a length of yarn across the back of the swatch and move the circular needle so that the point is back at the beginning of the swatch, right side facing you.
Continue in this manner until you have a swatch that is at least 4″ x 4″ (10 cm x 10 cm). You will want to make sure the edge stitches are tightened up, as they tend to be very loose.
You may clip the lengths of yarn that are carried across the back, or leave them intact so that you can reuse the swatch yarn in your project.
Do you have a stitch for an upcoming pattern you want to demonstrate but don’t have time?
I’m scheduling my recordings and will be including a series of How To videos for both knitting and crochet. These will be free to reference, in return for a credit within the pattern.