Add one extra YO (yarn over) to your DC and you have this stitch mastered! Make a chain of any length, in the 5th chain from the hook, YO twice, insert your hook into the next ST, YO and pull up a loop, YO and pull through two loops, YO and pull through two loops again, YO and pull through remaining two loops left on the hook.
Continue across the chain, CH 4 and turn. Just like the DC, the tuning chain counts as the first stitch.
I don’t personally use this stitch much on its own. It’s usually part of a shell pattern, or to fill in the valleys of a chevron. However, it’s still a good one to know!