Abstract: A machine for binding sets of sheets with a wire binding element of the kind having a series of curved prongs with points and roots. The machine comprises a holding mechanism for holding the binding element in a predetermined position. A selectively movable guide plate is located adjacent to and at a constant preset distance from the binding element points. The guide plate is also located to receive perforated edges of the sheets thereagainst so that the sheets' perforations can be aligned with the points in order to aid in guiding the perforated sheets into assembly with said binding element. A first adjustment mechanism is provided for moving the guide plate relative to the binding element points. The first adjustment mechanism permits the position of said guide plate to be adjusted relative to the points so as to maintain the constant pre-set distance between said guide plate and the points for any sized binding element.