My old club used to work with the Civil Air Patrol, supplying towplane, gliders and sometimes glider pilots to give cadets orientation flights. One disagreement over signals led to some pretty heated discussions.

Our club practice was to keep the wing on the ground until slack was removed glider pilot gave the thumbs up and the runner checked the pattern etc. He would then raise the wing. Rudders were waggled at both ends and if the runner felt it was safe gave the launch signal. The thought process was that it was easy for the tug pilot to see the wing's position. If the wing was down, stand by. CAP insisted that the wing should be raised to indicate the tug could take up slack citing their (and SSA's?) wing runner course. The problem was that the mix of tug and glider pilots varied. Sometimes one or both being ours, sometimes theirs. I've seen it done both ways. It seems to me that a takeoff commencing when the glider pilot isn't ready is less likely the way we did it. If the wing is up, the glider pilot is ready. But, when in Rome...

The FAA handbook says "Pilot ready, wings level — when the glider pilot is ready for takeoff, a thumbs up signal is given and the wing
runner will level the wing to the takeoff position".