What's the little button on the left side of my Macbook Pro do?

Just bought a 1993 4runner on the left side of the shifter is the od controll on the front of the shifter there is another button whats this for?

• Answer:

  There is a button other than the ECT mode button and it's called the shift lock. I've never used it before. I looked in my manual and it says that if you push that button it will cancel the shift lock that is normally cancelled by pushing on the brake. This would allow you to shift without pushing the brakes. This may seem obvious but the only other button I can think of is on the end of the shifter towards the front and it's the button that you're supposed to use when you shift in and out of park/reverse/etc. I found that it isn't necessary to push it to change gears on my 4runner ([edit] It's because it's broken). This button is the closest to the 0/D cancel button.