as a security shutter or door this enhanced strength may be selectively used to reinforce portions of the shutter such as a reinforced lower portion of the shutter for use as a vehicle barrier when used in this document u201c deployable slats u201d generally refer to those that exit the plane of the flat curtain rather than referring to deployability with respect to the action of simple up down rolling unrolling of a planar curtain shutter further shutters are referred to as rolling up and down in the present application but in other embodiments the shutter assemblies may be reoriented to produce a side to side opening closing action with the addition of appropriate load bearing rollers bearings or slides on the shutter edge this alternate construction is considered to be included whenever up and down motion is discussed only up down motion is explicitly discussed herein to reduce possible reader confusion typical shutters comprise a series of interlocked identical slats 10 as shown in a side view of fig1 the slats form a flat curtain that rides in and is retained at the edges in edge tracks 20 the slats are typically formed by aluminum extrusion and the side view of fig1 depicts a typical current extruded shape for the slats the strength of the curtain especially normal to the plane of the curtain is derived primarily from the cross sectional shape of the slats the prior art curtain does not provide strength enhancement as in the present invention where the strength enhancement is derived from the formation of structural shapes from the slats as the curtain is rolled down into place over the protected opening mcgregor in u.