Please note the following points to prevent the vehicle from rolling back unintentionally on a gradient.
Pull and hold the 
switch and press the accelerator. The parking brake will remain engaged and prevent any tendency to roll back down the slope.
switch and press the accelerator. The parking brake will remain engaged and prevent any tendency to roll back down the slope.You can release the switch as soon as the engine is delivering enough power to the wheels.
switch as soon as the engine is delivering enough power to the wheels.