When Red was teaching Thomas to ride broncs, what trick did he play on Thomas?
Red's plans for Thomas include using Thomas to make money for Red. Red tells him when to win and when to lose in order for Red to increase the gambling odds in his favor. All Thomas represesents to Red is a way to make money. He uses him, not caring what effect this has on Thomas. Red is greedy and selfish and manipulates Thomas to ride for the sole purpose of making money for Red. He is able to exploit Thomas because he knows Thomas needs him at first to teach him and provide him with horses.
Red wanted Tom to learn never to trust someone else with his gear, so REd cut the latigo and the cinch of Tom's saddle before Tom mounted. As Tom started to ride, The cinchs gave way and the saddle turned upside down.