Here are some examples of a bevel:
When a squared edge (an edge with a 90 degree angle) is cut off or rounded off, it has been bevelled. That edge is now called a bevel. A bevel of 2 milimeters is a very, very small bevel.
By the way, this sentence: "She is taking a wooden clamp which is composed of a handle and tongs,and the handle is getting a 2 mm bevel on all 4 ends."--is awkward. I strongly suspect that it was not written by a native speaker of English.