Butt hinges, also known as Mortise hinges, are a popular type of hinge frequently used in the United States, especially on doors. These hinges are constructed with two matching leaves of metal connected by a central pin and barrel system. One of the leaves is mortised, or recessed, into the door while the other is attached to the jamb. Proper installation of the butt hinge will result in the two leaves sitting flush against each other, allowing the door to fit perfectly flush with the jamb.

Butt hinges are commonly used throughout American homes, both for interior and exterior doors. To prevent corrosion that can disrupt hinge movement, stainless steel or brass hinges are often used for exterior doors. While butt hinges were once the standard for cabinet doors, their popularity has decreased with the rise of Soss Invisible and Poly Concealed hinges. While simple to construct and easy to use, the proper installation of butt hinges requires a router to ensure smooth mortising for a flush finish.