Leaks in concrete, brick or sheet pile structures can be sealed by injection. Cracks, construction joints and gravel nests and the like can cause leakage. The cracks are generally drilled obliquely with a rotary hammer. The bore hole must then be cleared of dust. An injection nipple is then placed in the borehole. This can be a blow, screw or sticky clip. Subsequently, injection fluid is pressed in under low or high pressure and the crack is filled. Depending on the object to be injected, the injection fluid can be rigid, flexible or swelling. The reaction time of the injection resin can also be accelerated by means of catalysts. Since injection work can only be assessed on the outside of the construction, these activities require a great deal of experience and knowledge.