A "Personal Fall Arrest System" is comprised of a full body harness, a connecting device and an anchor point. Before the system is used make sure you experience how the equipment works, make necessary adjustments and become comfortable and familiar with the system.
A full body harness provides support evenly over the shoulders, buttocks and thighs. This is important because it provides the best support against injury because of this distribution to the powerful parts of the body. Make sure it fits properly so that the D-ring is in the middle of the upper back, the waist strap is buckled, the leg straps are connected properly between the legs and all the buckles are securely tightened to the point where they are tight but they don't restrict movement. Make sure an experience worker or supervisor watches you the first couple of times.
Next, you hook it to a connecting device. This links you to a secure anchor point. Connecting devices are commonly lanyards and retracting lifelines. Lanyards are short ropes or straps which limit your possible falling distance and sometimes even have shock absorbers. Self-retracting lifelines have a drum-wound line allowing a wider range of movement. The braking mechanism quickly stops a fall.
Sometimes a fixed lifeline is used. There are two types - horizontal and vertical. Horizontal stretches across a work surface from one point to another and vertical hangs from an independent anchor point. They allow you to safely climb ladders. All connection devices are equipped with a locking mechanism that grabs the lifeline during a fall.
Sometimes "Bonsun's Chairs" are used with vertical lifelines. They are most often used when someone is working off of the side of a structure. Two independent lifelines are used - one for you and one for the chair.
When using any lifeline, make sure the anchor points are secure. Your weight creates significant force - up to 5000 lbs - and a proper anchor point is critical. Never use fixtures such as pipes. A solid structure is the only option.