On most TenPoint, Horton Crossbow Innovations, and Wicked Ridge Crossbows, the safety knob can be moved to the opposite side. 

The safety knob cannot be changed on ACUslide Series crossbows including the TenPoint Vapor RS 470, TenPoint Vengent S440, and the TenPoint Viper S400.  

If the safety knob can be changed on your crossbow model, please view the video Reversing the Trigger Safety Knob for detailed steps.