Herringbone knitting stitch
Overlapping pairs of stitches make dense diagonal strands.
Counted practice swatch
Cast on 20. On the RS knit two together through back loops but drop only the first stitch; on the WS purl two together but drop only the first.
Work the repeat
RS: repeat the overlapping knit pair until one stitch remains; knit the last stitch normally. WS: repeat the overlapping purl pair until one stitch remains; purl the last stitch normally.
Read the fabric
Keeping the second stitch on the needle gives the next pair its overlap. The fabric is dense: use a larger needle for the same yarn and measure this stitch itself.