Hi I was looking online how to fix my 3dsXL game slot without swaping a new unit. My problem was simple, I could load games but wont lock them in. They will pop up right away. 1. First remove the back cover of your 3ds by removing the 2 back screws 2. remove the back plastic panel; there are 5 visible screws, lift the two rubbers on the back to reveal 2 more screws, making a total of 7 (look on the cart entrance). 3.carefully lift the back plastic panel pivoting on the game cart. 4. if you want you can disconnect the L and R buttons by lifting the connectors. then we move to the game card slot, the way it works is really simple. Inside, the lock mechanism has 3 pieces to make it work. First the removable ones: springs and plastic rail guide (see picture) the other part is a metal pin inside the the slot on the left side, the is a little meta tab that you have to pull in order to reach it this metal pin goes in the rail guide on the plastic piece, mine was out so it wont lock. after just pull back the meta tab as this helps the pin to ride the guide, but don't push it to far as it could lock it. and that's it.