A trailing edge is the rearmost edge of an airfoil (wing, flap, rudder, elevator, etc.). It maybe a formed or machined metal strip or possibly a metal-covered honeycomb or balsa wood core material that forms the shape of the edge by tying the ends of a rib section together and joining the upper and lower skins. These trailing edges are very easily damaged. The majority of this type of damage can be avoided if care is taken when moving aircraft in confined spaces, and/or when positioning ground support equipment around parked aircraft. The trailing edges on some high-performance aircraft are almost knife edge in construction. You must take extreme care when working around these surfaces to avoid injury.

Figure 14-19.Balsa wood repair with nonflush patch.

Trailing edge repairs to all-metal construction assemblies and/or control surfaces are performed by using basically the same procedures outlined in the chapter titled "Aircraft Metallic Repair." A typical trailing edge repair to a sandwich construction assembly is shown in figure 14-20. 

You may use the lap or flush patch, depending on the size of the damage, the type of aircraft, and the assembly or control surface to be repaired. Normally, the flush patch is used on control surfaces to ensure aerodynamic smoothness.