Are you looking to install a block heater? Engines have what are called frost plugs located on the sides of the block. These are actually holes used in the casting process. Some blocks have one, some two, and some three...on each side. You can see these from under the car, or possibly through the wheel well on the explorer. You may have to remove something like the exhaust manifold or starter to get access to a particular soft plug. But most engines have at least one that is accessible without a lot of work. Keep in mind that if you are installing a block heater, they usually tell you which hole they want it in and what direction to point the element.