The problem of preserving geometric design conditions by the device of locks has been presented in the paper. The problem was illustrated by the alignment of the shaft flap bearing sleeves of the sluice on the navigable channel. The assembly design required the coaxial bearing sleeves with an accuracy of no more than 0.5 mm. Thanks to first – class measuring equipment and the author’s innovative solution (Axisymmetric telescope centring device No. EP12460083.4) protected by the European Patent Office it was possible to achieve this goal. The reference axis is determined by the axis of outside bearing sleeves previously brought to one level. The innovative device is mounted at the outside bearing sleeve on one side of the lock and the target plate is mounted in the axis on the outside sleeve on the other side of the lock. The aiming line of the telescope and center of the target plate determine the reference axis for other bearing sleeves. Thanks to the innovative solution the desired accuracy was achieved, measurement time was shortened significantly and safety conditions of persons performing measurements were improved. The invention may be applied to other similar cases.