Follow the 6' rule, gang. What we do need to talk about is the equipment. In English, the individual parts of the system, along with the connections between the parts, must each have a tensile strength of at least 5,000 pounds. Parts and the connections between parts must the sum of the parts is equal to each of the parts as individuals. It won't protect you if you have a system in place and then attach it to the building with a paper clip.
Lets do the easy stuff first.
And, surprise, surprise, it must be OSHA approved and be so labeled. These harnesses may feel more comfortable as a work platform, but in a fall can cause serious injuries to the back and parts of the body. We are, of course, assuming you survive the fall. The proper harness can make the difference. Next comes the lanyard.