A screen wiper for a motor vehicle comprises a wiper arm carrying a wiper blade and applying a wiping pressure, so as to urge the latter against the windshield of the vehicle as the arm is oscillated in the usual way across the windshield by a drive spindle, which carries a drive head on which the wiper arm is fitted. The wiper arm carries a guide bracket which, in the parked position of the wiper, cooperates with an engagement surface of a ramp fixed to the vehicle body, so as to lift the wiper arm and so relieve the wiping pressure. The guide bracket has an indexing claw which cooperates with a claw formed on the ramp to define a precise angular orientation of the wiper for fitting of the latter on to the drive head.