A wiper (22) has a length (L) which is divided into a distal segment (D), a middle segment (M) and a proximal segment (P). Wiper (22) has first and second wiper blades (26, 28), each having wiping faces (26c, 28c) in contact with a surface S and defining therebetween a channel (30). One or both of the blades (26, 28) have one-way water-passage formations thereon along the middle segment (M) of the length (L) thereof. Such formations, e.g., notches (34,36), are dimensioned and configured to permit passage of water through, e.g., the second blade (28), to the channel (30) when the second blade (28) is moving in a first direction, and to prevent passage of water through notches (34) when the second blade is moving in a second direction opposite to the first direction. Conversely, the first blade (26) formations, e.g., notches (34), permit water to pass through the formations when the first blade (26) is moving in the second direction and to prevent passage of water therethrough when the first blade is moving in the first direction. At least one intermediate blade (27) may be disposed between the first and second blades (26, 28) to divide the channel (30) into a first course (30a) and a second course (30b). A method of wiping a surface (S) includes controlled entry of water into the channel (30) and expulsion of water from the distal end (42) of the channel, assisted by a Venturi Effect and centrifugal force.
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