When installing a capture card on a 3DS, use the rights tools, work slowly, and follow an illustrated guide to make sure you don't break the device. Capture cards allow 3DS players to record their gameplay.
Use a size #000 screwdriver to remove the screws, a Dremel to cut the case and a high-quality soldering iron with a fine point. Also work very slowly, and check your progress regularly, as the 3DS has delicate parts that you can break easily.
Especially if it's your first time installing a capture card, you should follow an illustrated guide. 3DSCapture.com offers a guide with high resolution pictures. Click on the pictures to enlarge them, and compare your progress.