A bulldog clip is a device for temporarily binding sheets of paper together. It consists of a rectangular sheet of springy steel curved into a cylinder, with two flat steel strips inserted to form combined handles and jaws. The user presses the two handles together, causing the jaws to open against the force of the spring, then inserts a stack of papers and releases the handles. The spring forces the jaws together, gripping the papers firmly.
BULLDOG is a registered trademark of Setten IXL Limited in relationship to stationery equipment, however the term "bulldog clip" has largely become a genericised trademark for all varieties of binder clip. Its registration as a trademark in the United Kingdom dates back to 1944.