Often a rigid wire or, conversely, a soft rod or a thin pipe required to give the necessary bending of a specific shape and size. Often try to do it in a Vice or just pliers that threatens to ruin the material.
The same thing, but without injury, and much faster (especially if you want to bend more than once) can be done by making a simple pattern: from nails or screws, wooden lugs, or combinations thereof – shown in the picture sample.