Figure 8-7.  Towplane and glider signal due to release mechanism failure.  Since some gliders do not back release,  the glider pilot should  pull the release to ensure the towline is in fact released. Towplanes are usually fitted with a  variant of the Schweizer  or Tost glider tow hitch.  [Figures 8-8 and  8-9]  The hitch is  usually located at the extreme end of the rear fuselage below  the rudder. The specific rings used to at tach towlines to these  hitch types can be seen in  Figure 8-10 . The wing runner  must be familiar with the correct  method of attachment. If  the towplane has the Schweizer tow  hitch, it is possible for  the tow ring to rotate forward so that  it traps the sleeve that  locks the tow hitch in place. This may prevent the tow pilot  from releasing the towline.  [Figure 8-11] Glider: Release immediately Towplane rocks wings Glider cannot release Glider moves to left side of towplane and rocks wings Towplane cannot release After receiving signal that  glider cannot release,  towplane yaws repeatedly Figure 8-9.  A Tost tow hitch. Ring Hook Towhook closed Towhook open Failure of both towplane and glider  release mechanisms is  extremely rare. If it occurs, however, radio or tow signals  between glider pilot and tow pilot  should verify this situation.  The glider pilot should move down to the low tow position  Figure 8-8.  A Schweizer tow hitch. Figure 8-10.  Examples of Schweizer and Tost tow rings. 8-9 Schweizer ring Tost ring