According to Crochet Today:
“Tunisian Knit Stitch makes a crochet fabric that is even denser than Tunisan Simple Stitch.
You will need a longer hook to work larger Tunisian patterns, but a regular hook works fine for smaller items and practice swatches. Begin by making a foundation chain, then work one row of double crochet. Turn and begin working the first Tunisian knit stitch row.”