One of the immortal Elizabeth Zimmermann's “unventions,” this sock construction makes it easy to re-knit the soles and heels when they wear out.
"The item, hot from the griddle, which I now unveil is the Moccasin Sock; the Breakhrough Sock, the Not-To-Be-Ground-Down Sock; the Eventually Totally Re-footable Sock. Call it what you will; all the above tentative titles apply.
If you are a maker and mender of socks you have shared with me the heart-break of finding holes right next to the places which have been carefully strengthened with nylon. Many of the offending holes are right under the heel, just past the point where the heel-turning was completed and knitting was continued around, minus nylon."
Knitter's Almanac or Knitting Around