I know how to knit into the back loop, but purl 2 through the back loop. I'm not sure how to. What does this decrease do? How does it slant?
The slant won't be noticeable on the purl row, but on the knit row would look like ssk. Go to the Glossary and find p-b for purl through the back loop. Watch the video and try it, then work on a p2tog tbl.