In DIY stores, you will find a multitude of different keys, each with a very specific use. The flat key allows you to screw or unscrew nuts, screws and bolts with hexagonal or square heads.
The eye wrench has an eye, also called a socket, with a variable size of 11 and 13 mm. There are also DIY wrenches for specific use, such as the Allen key for hexagonal head screws, or the Torx key for six-pronged torx screws.