They were knitted on a Brother 860 in 2:1 rib at SS4/4. For the heel opening I put half the needles in hold and knit one row at SS8/8 on the other half, then 10 rows in waste at SS4 then 1 row on these needles at SS 8/8, put these needles in hold and knit the remaining needles at SS 4/4. I think this might be the bridging technique. I finished in the same way and then latched the stitches one through the next for a stretchy finish. They are in fingering weight sock yarn. Thank you for the idea.