Precautions have to be taken to prevent these distinctive marks from appearing. Firstly, there are various methods if you're sanding a stained or unstained floor. Equally, different kinds of timber have to be treated in various ways and perhaps even different ages of wood will react to sanding in various ways.
An expert will know which type of equipment is required and furthermore, will have it at their disposal. Suitable, high quality floor sanders aren't cheap and you can not necessarily just go and hire one. A good sander needs weight and power. You want the right tools for the job.
So instead of hiring the sander and risking your beautiful hardwood floor, why don't you hire professionals to perform the sanding job in its entirety? You can then be assured that your flooring won't be damaged and will wind up looking as great as it's ever done.