B A D C W ind  W ind  W ind  W ind  Sink Lift W ind  Figure 10-22.  Ridge rules. Figure 10-23.  Avoid sink on the downwind side of spurs by detouring  around them. but when done properly, a rapid climb in the thermal can be  made well above the ridge crest, where thermaling turns can  begin. Even when well above the ridge, caution is needed to  ensure the climb is not too slow as to drift into the lee-side  sink. Before trying an S-turn, make sure it would not interfere  with other traffic along the ridge.  [Figure 10-24] A second technique for catching thermals when slope soaring  is to head upwind away from the ridge. This works best when  Cu mark potential thermals, and aids timing. If no thermal is  found, the pilot should cut the search short while still high  enough to dash back downwind to the safety of the slope  lift.  [Figure 10-25] As a final note, caution is also needed to avoid obstructions  when slope soaring. Obstructions include wires, cables, and  power lines, all of which are very difficult to see. When  flying at extremely low altitudes along the ridge (tree top  level), the glider and pilot may be placed at a high risk of  collision with wires. Ensure an adequate reconnaissance has  been completed when flying at these altitudes. Aeronautical  charts show high-tension towers that have many wires  between them. Soaring pilots familiar with the area should  the glider is turning toward the ridge. Speed is also important,  since it is easy to encounter strong sink on the sides of the  thermal. It is very likely that staying in thermal lift through  the entire S-turn is not possible. The maneuver takes practice,  Obstructions 10-14