Modern sewing machines use either oscillating or rotary hooks to snag the upper thread, wrap it around the bobbin thread, and create stitches.
The lock-stitch originated in 1846. An upper thread source was drawn down through fabric using a needle, forms a loop on the needle's back. A shuttle or today a hook device picks up this thread from the needle. As the needle rises, the bobbin thread and upper thread form a knot inside the fabric.
There are two common types of hook systems. Oscillating hooks move back and forth, while the rotary hook moves round and round twice for each stitch.
Hooks may be mounted horizontally common to top loading machines, but they can also be mounted vertically for front loading or side loading.