A paper knife or letter opener is a knife-like object used to open envelopes or to slit uncut pages of books. Electric versions are also available, which work by using motors to slide the envelopes across a blade. These have the advantage of being able to handle a greater volume of envelopes, but the blade can slice into the contents of the envelope and damage them.
Letter openers may be composed of wood, metal, plastic, sometimes even ivory, or a combination of materials. Some modern openers have a hidden razor blade inside a plastic handle.