6. Under threading: In each bobbin case there is a slanting slot and a spring. Insert the bobbin into the bobbin case so that the thread comes around the bobbin and turns back to lie in the slot. Now guide the thread through the slot and below the spring and pull out a length of thread.

The filament could be stretched ever further and it did not go back to its original length. This stimulated the group to concentrate on textile fibers. The term nylon was chosen for the fiber and it was called the miracle fiber for several years. The first nylon was referred to as type 6,6. The numbers derive from the fact that each of the two chemicals used in making this type of nylon has six carbon atoms. Nylon type 6, 10 was developed at the same time and it is composed of one chemical with six carbon atoms per molecule and ten carbon atoms per molecule for the second chemical. Nylon 6, 6 was considered desirable for apparel and selected home furnishings; nylon 6, 10 was used in making brushes, and similar items. In many countries nylon is identified by term Polyamide.