According to an example aspect of the present invention, there is provided an apparatus for mounting a device on a manipulator, wherein a second unit is adjustably attached to a first unit so that it is movable in at least one direction with respect to the base plate and wherein the first unit has at least a locked position and an open position, the mounting rail being movable with respect to the first unit when the first unit is in the open position and wherein the mounting rail is fixed with respect to the first unit when the first unit is in the closed position.