A two-piece paper fastener includes a prong base with two prongs extending from two ends of a top surface of the prong base. Each of two sides of the prong base has a first flange folded toward a bottom surface so as to define a rounded side. A compressor with two holes through which the two prongs extend and two retainers are slidably mounted to the compressor. Each of two sides of the compressor has a second flange folded toward a bottom surface of the compressor so as to define a rounded side.

A device is provided for binding together sheets of paper formed with two or more spaced holes and attaching the same to a folder or the like. The binder preferably is injection molded of a semi-flexible material and is formed with a flat backing plate and at least a pair of stems which initially are parallel to one another and perpendicular to the backing plate. The stems are spaced apart by a distance equal to the spacing between the holes in the paper and are formed with co-operating male and female elements along the length thereof which allow the stems to be folded one against the other in locking engagement. Each stem is provided with a hinged stop at the free end thereof, which stop folds in against the stem while papers are being inserted or removed and swings out perpendicular to the length of the stem to prevent accidental separation of papers from the stem. Extension pieces are connectable to the ends of the stems and are provided with stop means at the ends thereof. The extension pieces allow a group of papers to be transferred quickly from the stems to the extension pieces in order to remove one or more inner sheets and then replace the top most sheets without disturbing their alignment.

A folder and fastener for retaining perforated sheets are provided with a fastener travel limiter secured on the inner surface of the upper flap of the folder. The fastener comprises a flexible tubular member attached to the inner surface of the lower flap of the folder and providing two ends extending through the sheet perforations, and a stiff closure element having ends releasably engaging the flexible member ends. The travel limiter engages the closure element and defines a travel space for it, permitting free travel of the closure element parallel with the upper flap inner surface during opening and closing of the folder.

A paper fastener includes a base having two end legs for engaging through sheet materials to be clamped and having two side panels bent relative to the base and two outer flanges folded relative to the side panels and shielded by the side panels. A bar includes two end orifices for receiving the legs of the base, and includes two side flaps bent relative to the bar and two outer flanges folded relative to the side flaps and shielded by the side flaps of the bar. Two retainers are slidably engaged on the bar for securing the paper sheets between the base and the bar.