Fall arrest lanyards are an essential component of a personal fall arrest system and are used to protect workers from falls while working at heights. A fall arrest lanyard is a flexible rope or webbing that connects the worker's harness to an anchor point or lifeline. 

There are different types of lanyards, including shock-absorbing lanyards, self-retracting lanyards, and adjustable lanyards. Shock-absorbing lanyards are designed to reduce the impact of a fall by extending the length of the lanyard and absorbing some of the shock. Self-retracting lanyards are designed to automatically retract when not in use, while adjustable lanyards can be adjusted to different lengths to accommodate different work situations. 

It is essential to choose the right type of lanyard for the job and ensure that it is properly inspected and maintained before each use to ensure worker safety.