The European XFEL will generate extremely short and intense X-ray laser pulses of high coherence and nearly diffraction-limited divergence. Guiding these X-rays beams over a distance of more than 1 km to the experiments requires an extreme precision in pointing stability of beamline components like mirrors and gratings and also a control of the divergence of the beam. The specifications of the X-ray mirrors that will be able to transport, distribute and focus the beam are quite challenging. The European XFEL mirrors for the beam transport are 950 mm long and the optical surface specifications are 2 nm Peak-To-Valley. Some of the mirrors will have bending capabilities in order to focus the beam in the right position and with nanometer accuracy. This is implemented using a mechanical bender that will ensure stability of the optics in the nanometer range and will also offer the possibility to correct for mechanical or temperature drifts. We present here the characterization of a mechanical bender that was done using two instruments, a Large Aperture Fizeau interferometer and a system of three capacitive sensors. The bender is designed in a way that the mirror is hold with clamps on both ends and a symmetric torque is applied on the clamps, inducing a cylindrical shape on the mirror surface. Several long-term stability measurements were done, as well as the characterization of bending capabilities. The parameters retrieved from the measurements are the sagitta and therefore the radius of curvature for different bending positions. The behavior of the variation of the shape of the mirror was also studied. The information gathered from our measurements will be used to optimize the final design of the bender.