Slat bending is the distortion of a shutter slat that bends, bows or twists. It can come from use, the sun, a knock or an attempt to force it.
You can recognise it because the slat is no longer straight: it bulges in the middle, rubs in the guide rails or catches as it goes up. A bent slat is often the cause of a jammed shutter.
It is also a method of attack. A slat is a long, thin strip, and if it is pushed in the middle it gives way until it comes out of the guide rails. That is why our shutter security system fixes a 4 mm steel T-profile, which does not bend, to the bottom slat and locks it into the wall at both ends.