Thank you for your help!
Looks like crochet…
It goes by several names, but it’s (sc, ch 1) across (you may have to skip the last ch-1 and sc into the last stitch) then the next row is (ch 1 to turn, sc in ch-1 sp, ch 1) across. In other words, always work into the chain-1 spaces and chain 1 between sc. It makes a nice fabric, lighter and more flexible than straight sc.