nice machine. you plough with the draw bar lock disengaged. as far as i am aware it is there to make transporting the machine between jobs easier by locking the plough in place. you use the two small bolt on stops to limit the swing of the draw bar during ploughing but i cant really describe how to set them as it depends on what sort of ground you are working on and i don’t know if you set it differently when using a digger plough as apposed to a greyhound.