To attach the fabric to the airframe, first pre-apply two  coats of adhesive to the structure at all points the fabric is  to contact it. (It is important to follow the manufacturer’s or  STC’s guidance as all systems are different.) Allow these to  dry. The fabric is then spread over the surface and clamped  into position. It should not be pulled tighter than the relaxed  but not wrinkled condition it assumes when lying on the  structure. Clamps or clothespins are used to attach the fabric  completely around the perimeter. The Stewart System STC  does not need clamps because the glue assumes a tacky  condition when precoated and dried. There is sufficient  adhesion in the precoat to position the fabric.  The fabric should be positioned in all areas before undertaking  final adhesion. Final adhesion often involves lifting the  fabric, applying a wet bed of cement, and pressing the fabric  into the bed. An additional coat of cement over the top of  the fabric is common. Depending on the process, wrinkles  and excess cement are smoothed out with a squeegee or are  ironed out. The Stewart System calls for heat activation of  the cement precoats through the fabric with an iron while  the fabric is in place. Follow the approved instructions for  the covering method being used. Once the fabric has been glued to the structure, it can be  made taut by heat shrinking. This process is done with an  ordinary household iron that the technician calibrates before  use. A smaller iron is also used to iron in small or tight places.  [Figure 3-21]  The iron is run over the entire surface of the  fabric. Follow the instructions for the work being performed.  Some processes avoid ironing seams while other processes  begin ironing over structure and move to spanned fabric or  vice-versa. It is important to shrink the fabric evenly. Starting  on one end of a structure and progressing sequentially to the  other end is not recommended. Skipping from one end to the  other, and then to the middle, is more likely to evenly draw  the fabric tight.  [Figure 3-22] Fabric Heat Shrinking Figure 3-21.  Irons used during the fabric covering process.  Figure 3-22.  An example of a wing fabric ironing procedure designed to evenly taughten the fabric. 3-17 1 Begin on one end 2 Move to the opposite side 3 Switch from side to side 4 End in the middle