The safety of existing concrete slabs against shear may be insufficient for several reasons such as design and construction errors, structural modifications or increased loads. Moreover, the knowledge about shear design has significantly increased over the last few decades and therefore, even structures correctly built according to older codes may not comply with newer codes based on the latest state of the art. This paper presents a method to enhance the one way shear strength of RC slabs or beams by postinstalled shear reinforcement. The reinforcement is bonded into inclined drilled holes from the bottom of the slab and anchored at the end by anchor heads. Compared to other methods, this has the advantages that the strengthening work can be carried out from one side of the structure and that the dimensions of slab are not modified. A series of beam shear tests has been performed to assess the influence of the geometric layout of the reinforcement as well as the anchorage. The tests show a clear strength increase due to the postinstalled reinforcement.