Shutter slat end retention system

A rolling shutter assembly comprising:

• a curtain comprising a plurality of engaging slats that engage one another, each slat having a first end and a second end, a first edge and a second edge, and a profile width;
• a guide track in which the first ends of the plurality of engaging slats travel as the curtain is moved across a building opening by an operator, the guide track having a lengthwise cross-section comprising a channel having a channel width, a channel depth, and an opening in the channel width, the opening defined by first and second retention fins spaced an opening distance apart, the opening distance sufficient to accommodate a slat end so as to allow the first ends of the engaging slats to travel the length of the guide track in the opening,
• wherein a plurality of slats each have a first end comprising an end retention device, each end retention device comprising:
• a fastener attached to the first end of the slat, the fastener comprising a shaft having a shaft diameter and a shaft length, wherein the shaft extends for the shaft length from the end of the slat into the channel, and a head having a head width at the end of the shaft away from the first end, the head disposed in the channel;
• a freely rotatable washer disposed inside the channel and around the shaft, the washer having an outer diameter greater than the profile width and less than the channel width, and comprising an aperture having an inner diameter that is at least twice the shaft diameter but smaller than the head width, the aperture of the washer disposed around the shaft such that the washer is capable of sliding along the shaft length, canting about an axis perpendicular to the shaft length, and moving perpendicular to the shaft length when the fastener is attached to the slat end;
• wherein the head and washer are disposed in the channel of the guide track when the slat end having an end retention device is retained by the guide track,
• further comprising a shutter casing in which the curtain is rolled when the shutter is retracted, wherein the washers of the end retention devices move about the respective shafts such that the washers reposition themselves when contacted by one another when the curtain is rolled.