Crack filling involves the insertion, injection or embedding of liquid substance into the cavities, pores and cracks of a solid object, such as concrete, soil or other material, in order to reinforce and waterproof it. Crack filling is a complex process, which should be divided and assessed based on different phases. The precondition for successful crack filling is the thorough examination of the crack, focusing on the causes of fracture, its effects on concrete, its type, width, length, condition, changes in width, dampness and the strength of water current. Next, concrete technology should be analysed and appropriate restoration measures should be selected accordingly. These analyses help decide which type of injection (rigid bond, waterproofing, elastic or filling) should be used and what materials should be chosen.