A magnifying glass (called a hand lens in laboratory contexts) is a convex lens that is used to produce a magnified image of an object. The lens is usually mounted in a frame with a handle. A magnifying glass can be used to focus light, such as to concentrate the sun's radiation to create a hot spot at the focus for fire starting. Keep your letter opener in a convenient place where you're most likely to use it, such as where you normally sort and open your mail. Pick up each envelope one at a time and slide the letter opener through the top crease. Insert the sharp side of the letter opener inside the crease, not the handle.
