There are two types of slide fasteners— separating and nonseparating. A nonseparating, type A, slide fastener is used where only a small area needs to be opened; for example, the opening in a parachute bag. A separating slide fastener, type B, is used in areas where it is necessary to spread the opening for easy access, such as on a jacket or the legs and waist of an anti-g coverall. To determine the size or service weight of a slide fastener to be installed on a fabric assembly, consider the weight of the material and the stress that will be applied. The size range and services of slide fasteners are as follows: 1. Size 0 - light service 2. Size 1 - light to medium service 3. Size 2- medium service 4. Size 3- medium to heavy service 5. Size 4- heavy service Materials used inslide fastener construction vary from plastic and nylon to cotton, rubber, and metal. There are two common grades of slide fastener chains. Grade I is of brass construction and Grade II is made of other metal alloys or synthetic materials. In most instances, however, you will be concerned with fasteners that have been constructed from cotton fabric and metal parts. A closely woven cotton fabric is commonly used for the tape of a slide fastener; match the color of this tape to the main fabric color when installing a slide fastener. On certain items of survival equipment using slide fasteners, it is mandatory that the slider remain stationary where it is positioned on the chain. An accidental opening in flight of an equipment container or item of flight clothing could cause a lot of trouble for the aircrewman. Unintentional opening of a slide fastener that requires positive security is prevented by using a locking style L slider. Illustrated in figure 10-20 are two common types of locking style L sliders: the pin type and the cam type. The pin type is designed to lock when the pull tab is pressed flat onto the chain, thereby inserting its pin between two teeth on one side of the chain. The cam type is also designed to lock when the pull tab is pressed flat onto the chain, thereby causing friction between the chain and the cam. This action prevents any movement of the slider. Slide fasteners installed where the movement of the slider is not critical may be equipped with a style S, standard nonlocking slider. The style S slider is normally used on slide fasteners where accidental openings do not create a problem. The length of a slide fastener is determined by the amount of closure required. When ordering slide fasteners from class 5325 of the Federal Stock Catalog, you need to refer to the dimension column, which lists both the length of the chain and the width of the tape. The size of a slide fastener is referred to as its service weight. Activities should specify the brand of chain for which stops and sliders are required (Talon, Crown, or any other make). Slide fasteners in stock are supplied in the nearest length ordered. When received, you can cut the chain to the desired length; stops can be salvaged and reused on the cut chain. SEAMS AND KNOTS A variety of seams and knots are presented in the following text. HAND-SEWN SEAMS This is the age of great technological advancements and man has come to rely heavily on the conveniences that technology provides. As you know, almost everything you do involves the use of a machine. From the housewife with her automatic dishwasher and the computer that pays you regularly twice each month to the sewing machine you use to repair articles made from fabric, technology is involved. Very few people in our society have the opportunity to use hand skills; therefore, they search for hobbies, such as model aircraft building, carpentry, and leather crafts to satisfy this desire. You are fortunate because your job involves using both hand and machine skills. Very few people get the opportunity to work with raw and finished materials and have creating, fabricating, and repairing as part of their job. In your particular situation, not only do you use your hands for tying knots and packing life rafts, but you also use your hands to take the place of a sewing machine. By now you have seen that sewing is perhaps the most useful skill the fabrication and parachute specialist should develop. Few fabric maintenance jobs are performed without some kind of sewing. Although, from your experience, you know that most sewing is done with a machine; you also know there are occasions when machine sewing 10-20