You need a drill to drill holes into things, in my case I was drilling holes in the wall, so that's a drill, you need an electric drill. A spirit level helps you to check that things are level, either horizontally or vertically,. You don't want your shelves to be wonky, because if they're wonky stuff's gonna fall off and they're just gonna look terrible. It's a good idea to wear goggles, protective goggles to protect your eyes when you're doing this. If you want to look like a real DIY expert, you can put the pencil behind your ear instead of a tape measure.