Breaks on gliders kan be very different things.
On scale glider you will normally find something getting up from the wings inducing drag - like
But it is not so common on competition RC gliders. Use of flaps and ailerons as breaks are more common in my world.
Ailerons and flaps are programmed to work
- together with elevator.
- all aileron
- camber and reflex for thermal and speed flightmodes
- start mode (when pulling with catapults or winches)
- breakes
There are lost of videos showing the modes and how to program with differet brands of radios.
One short example - not a competition glider - just a foamie - but something similar in programming.