Installing Christmas lights on a roofline can be a little tricky, but with the right tools and techniques, it's not too hard. First, make sure you have the right type of light strands - ones that are meant to be outdoor lights. You'll also need an extension ladder and a good pair of gloves to protect your hands. Once you've got all of your supplies, you can start by attaching the lights to the roofline with nails or clips. Make sure to space them evenly and in a pattern that looks good. And don't forget to check the bulbs to make sure they're working properly!