Direct sunlight or dirt can build up on blades as films as they travel on the road to wipe the windscreen and hence require frequent washing with a mild detergent. Lifting of the windshield and the wiper and the blade must be checked now and then because the sun and the environmental factors cause the rubber to dry up and crack and split. In the case of hardening of rubber or appearance of cracks, then the material is no longer useful, and should be replaced. If the surface appears clear, dampen the glass with water, switch on the wiper to go through several cycles and then switch it off; blurred streaks suggest that it is time to replace the wiper blades. The movement of this wiper causes the various fasteners to loosen and it is recommended that these are checked and tightened as it is during the blade checks. When examining the front wiper blade, the blades have to be parked in a specific position and this is usually done by running the wipers and turning off the ignition at the preferred location. Turn the blade up a little and pull the retaining lever to unlock it, then withdraw the wiper arm from the blade and, while doing so, try not to put stress on the spring lock. Set and adjust the new blade on the wiper arm hook, ensuring you hear the 'click' sound that means that the blade is optimally fixed onto the hook. For rear wiper blade replacement, use the first stages of this method to position the blades, than, with a small screwdriver, push the retaining lever in and remove the blade from the wiper arm stud. To install you simply push the new blade over the stud till it fits. To change wiper elements, place a slit of a screwdriver between the wiper blade and the element and while pressing on the element apply torque clockwise to unlock the claw and remove the element. On the later models needle nose pliers should be used in order to remove as well as install the blade. Insert the new element into the second retaining claw and then through the rest of the claws until it reaches the end; at which the new element is bent back into the claw at the end of the blade.