You don't have enough space to rotate the wrench a full circle, so you can only turn the wrench little by little at a fixed angle in the corner. At this time, you will find that hexagons have more advantages than squares.
One corner of a square is 90 degrees, and the center must be rotated 90 degrees to restore the shape, while one corner of a hexagon is 60 degrees, and the shape can be restored by just choosing 60 degrees. When turning the wrench, turning the wrist 60 degrees is more labor-saving than turning it 90 degrees, and it takes up less space.
Compared with hexagons, the single side length of an octagon is shorter than that of a hexagon for the same screw head area. The action area between the octagonal bolt and the wrench is smaller, and it is easy for the screw head to be rounded.
Therefore, for standardized bolts, hexagonal bolts are selected instead of square or octagonal ones.
In addition to standard hexagonal bolts, there are also some non-standard parts, such as rectangular screw heads or bolts with pentagonal screw heads.
This is a process accessory with special needs, and it must be installed with specially customized non-standard tools.