Shutter slat configuration

A slat configuration for a shutter assembly comprising in combination, an extruded hollow body generally rectangular in cross section having two interlock members extending from opposite end surfaces to form mating tongue and channel interlocking elements respectively and one side having an outer zig-zag surface configuration providing a plurality of at least three ribs on each slat, having in said hollow body three successive closed cell regions formed by two integral panel members extending across the hollow body from wall to wall substantially at rib positions with the intermediate cell longer than the outer two and formed with internally extending flanges near each end thereof defining a central compartment with slots at either end thereof wherein the channel interlock member comprises a half cylindrical structure from which extends an L-shaped extension substantially closing the half cylindrical structure so that entry of the interlock tongue member is only permitted from the ends of the slat and wherein the hollow body terminates in two end pieces one comprising said L-shaped extension substantially perpendicularly disposed to the side walls and arranged to meet face to face to form a substantially weathertight crease along the zig-zag surface directly below an adjacent said rib when two adjacent slats are interlocked in closed position, thereby to allow rain to run downwardly off the zig-zag outer surface ribs without penetration to the inside of an assembled shutter configuration of a plurality of adjacent slats.