A binder clip, or a banker's clip or foldover clip, is a simple device for binding sheets of paper together. It leaves the paper intact and can be removed quickly and easily, unlike the staple. The term bulldog clip is used in the United Kingdom and Canada to describe both this invention and an older device with the same function, which is stronger and has rigid rather than folding handles. It is also sometimes referred to as a "handbag clip" because, when not in use, its clip can be up to look like a handbag.
Characteristics and methods of use
A binder clip is a strip of spring steel bent into the shape of an isosceles triangle with loops at the apex. Tension along the base of the triangle forces the two sides closed, and the loops prevent the sharp steel edges from cutting into the paper. The loops also serve to hold two pieces of stiff wire, which are used as handles and allow the clip to be opened. The two slots cut in each loop are shaped so that the wire handles can be folded down once the clip has been attached, and the spring force of the wire holds them down on the surface of the paper. This holds the clip relatively flat, for easier stacking of paper. One handle can also be folded down while the other remains up to allow the stack of papers to be hung up. The handles can also be removed altogether by squeezing them sideways and pulling them out, allowing for more permanent binding. As compared to a paper clip, the binder clip is able to bind sheets of paper more securely, and is also resistant to rust.
There are several sizes of binder clips, ranging from a base size of 5 millimetres (0.2 in) to 50 mm (1.97 in). The sheet steel portion is customarily black oxide coated, but a variety of decorative painted color schemes are also available. The sheet steel portion is occasionally made of stainless steel, the more typical spring steel can also be finished in nickel, silver or gold. The handles are normally nickel plated.
The binder clip is in common use in the modern office. It can hold a few to many sheets of paper, and is usually used in place of the paper clip for large volumes of paper. Various practical (and sometimes whimsical) alternative uses have been proposed. These include holding pieces of quilt together, creating a "beer pyramid" in a refrigerator with wire shelves, serving as a bookmark, a cheap alternative to a money clip or preventing computer cables from slipping behind desks. Smaller sized clips have been commonly used as "quick fix" fitting and sizing solutions in the fashion industry.
The binder clip was invented in 1910 by Washington, D.C., resident Louis E. Baltzley, who ultimately was granted U.S. Patent Number 1,139,627 for his invention in 1915. At that time, the method of binding sheets of paper together was to punch holes in them and sew them together, making it tedious to remove a single sheet of paper. Part of the original binder clip patent drawing was used as the official cover page of the Binder Clips Fans 
Baltzley invented the binder clip to help his father, Edwin Baltzley, a writer and inventor, hold his manuscripts together easily. While the original design has since been changed five times, the basic mechanism has remained the same.
Baltzley initially produced his invention through the L.E.B. Manufacturing Company. These earliest binder clips are stamped 'L.E.B.' on one side of the sheet steel. Manufacturing rights were later licensed to other companies.