This chapter summarises the topics previously discussed in Chapters 2-8. The objective is to illustrate how to create a computer code that simulates a flow of solid particles in a fluid. First, a model is shown that accounts for the motion of particles due to various particle-fluid forces introduced in Chapter 2. Later, it is emphasised that the particles may collide, and this can be described using the techniques mentioned in Chapters 3-8. Finally, a new problem is introduced (not considered in the previous chapters) – collision detection. This issue is crucial for deciding which particles flowing in a system could potentially collide during a time step. The chapter also unveils an algorithm in which the collision detection mode is implemented.