Since this is a now 10 years old machine, don't get discouraged if you have some trouble with screws, specifically the longer screws in the upper case. I carried this machine with me everywhere for four years of college before retiring her, she's been twisted, dropped, sat on, etc. If your MacBook has been through what mine has you might run into the same issues. For me the top left screw sat below flush after being unscrewed and wouldn't pull up magnetically. I had to put light pressure on the case around the screw and use a pair of tweezers to grab the screw head and pull it out. Some gunk had built up at the bottom of the screw making it impossible to pull out magnetically. Be patient putting these upper case screws back in, over long periods slight deformations occur in the structure, so the screws won't line up quite as well as they used to. You shouldn't have to twist hard for the screws to go back in, try slightly pushing the bottom case up/down/left/right if you're having trouble. Great guide!