What is the function of the tractor’s middle lift arm (“the third point”)?

1. To prevent vertical freedom of movement of the arms and of the tool.
2. To secure the harnessed tool with special security chains.
3. Correct answer: To prevent sideways freedom of movement of the arms and to prevent the tractor turning.
4. To lift the tool a few times to maximum height in order to ensure that the tool is properly harnessed.

WhyThe middle link (the third point) keeps the lift arms and the implement from swinging sideways.