I am using an old Macbook Pro as a monitoring station for our servers and some other minor tasks. I also have an external screen set up with this to better accommodate all the terminal windows and such. The computer is placed in such a way that I only need to use the external screen and would like the internal screen shut down. This turned out to be slightly problematic however.
Normally when you want to achieve this you simply close the lid on the MBP and then press something on an external keyboard or mouse and the computer would understand that only the external screen should be used. Since this computer is running 24/7 during weekdays I was slightly hesitant to do this since the MPB gets hot even with the lid open.
After a little searching and fiddling about I found a great tip that simply was to place a normal fridge magnet on the right speaker of the MBP. This effectively makes the MBP think the lid is closed and lets you keep working as usual with the lid opened. Sadly this was a while ago and I lost the source of the tip (if someone knows please leave a comment), but as the placement of the magnet was a bit different on the mid 2007 MBP I'm posting a helpful image for the people who wants to try this.