Strobel Sock or Strobel board
What is a strobel bottom of a sneaker? The Strobel is the fabric or non-woven material used to finish the bottom of a shoe upper. The worker uses a Strobel machine to make a Strobel stitch to attach the Strobel board to the upper.  It was invented by a guy named Strobel. Almost all athletic shoes made by Nike and Adidas are made by the strobel process.

 Strobel shoe Being Stitched

Shoe Lasting

How Shoes are Made PDF ebook

You can read more about Strobel bottoms and lasting in this article. Shoe Lasting.
You can learn more about many other types of lasting and other shoemaking procedures in the ebook. How Shoes Are Made.