We have now proceeded as far as the finished yarn. Sometimes, however, when a particularly strong thread is desired, or in case of fancy designs, it is desirable to twist two or more threads of yarn together, this being known as two-ply, three-ply, etc. Various effects are obtained by twisting different yarns together, and sometimes worsted and cotton strands are twisted together. The operation is done on a frame similar to the spinning frame. [Illustration: _The Barber Knotter_] [Sidenote: _The Barber Knotter_] In these and subsequent operations the Barber Knotter, a little device worn on the hand of the operative, has enormously increased efficiency. By a single motion an entirely unskilled girl can knot and cut off evenly the ends of two threads. 3. WEAVING GRAY GOODS [Sidenote: _Principle of Weaving_] The modern power loom represents one of the most remarkable achievements of industrial development. Into its perfection have gone the inventions and improvements of centuries, and volumes could, and have been written on the subject of modern weaving. Nevertheless, the old-fashioned hand-loom has not yet gone out of existence, and still finds its use in the development of new designs. [Illustration: _Spooling_] Weaving is, of course, the process whereby yarn is made into cloth, and its fundamental principle is that of the warp and weft structure. In its simplest form this means that a series of threads are stretched parallel to each other, thereby forming a warp. A second thread, called the weft, is then passed over the odd and under the even warp threads, and back again under the odd and over the even. In this way a cloth fabric will gradually be built up. In most cases the process has become considerably more complicated than this, but there are even now certain materials, such as calico, which retain the elementary weave. The actual weaving, that is, the passing of the shuttle carrying the weft thread over and under the warp threads, has now been reduced to an entirely automatic process, even with the most complicated designs, but the preparatory work still entails a large proportion of hand labor. [Illustration: _The Creels_] [Sidenote: _Spooling_] The first operation consists of winding the yarn from the bobbin on to spools, each containing the same length of yarn. This must be done with care or considerable waste will result. [Sidenote: _The Creel_] The next step is to place these spools in a rack or creel where they fit on glass bearings so that they may be arranged in the proper order and run through the warper on to the section beam. The latter is a large roller several of which are combined to form a beam. The beam is the name given to the roller which is placed in the loom to deliver the warp threads. [Sidenote: _Sizing_]