The side view shows the catch at the right hand side of this photo. Inserting the screwdriver pushes the catch backwards - so only insert it enough to move the plastic back by the depth of the catch. A couple of mm or so. The weight cannot be released until the coupling screw underneath the tender. A similar catch arrangement exists, and the catches on both sides have to be pressed in in order to lift the weight out. This is easy with a pair of small, thin-nosed pliers.