The type of carpet that is envisaged to be produced in the factory has got two main parts; the backing and the face. Each part can be made from different kinds of materials depending on the chosen design and quality. The backing can be jute or cotton. The face is mostly from acrylic. The yarn is put on a creel (a bar with skewers) behind the tufting machine, and then fed into a nylon tube that leads to the tufting needle. The needle pierces the primary backing and pushes the yarn down into a loop. Photoelectric sensors control how deeply the needles plunge into the backing, so the height of the loops can be controlled. A looper, or flat hook, seizes and releases the loop of yarn while the needle pulls back up; the backing is shifted forward and the needle once more pierces the backing further on. To make cut pile, a looper facing the opposite direction is fitted with a knife that acts like a pair of scissors, snipping the loop. This process is carried out by several hundred needles (up to 1,200 across the 12 foot [3.7 ml width), and several hundred rows of stitches are carried out per minute. One tufting machine can thus produce several hundred square yards of carpet a day. The process does not produce wastes that can be harmful to the environment.