The purpose of this manual is to give to the designer the tools to simulate the behavior of a twin-tube shock absorber on the computer. The designer will thus have the opportunity to size the damping characteristic of the shock absorber before practical realization in the laboratory of a working sample. He will also have the opportunity to evaluate in advance the accelerations produced by the attachments to the vehicle and the suspension system, this is very important as it is directly related to the noise perceived inside the passenger compartment.This publication is also dedicated at those who are interested in understanding the fluid dynamic functioning of the shock absorber.