of side walls 74 76 and end wall 78 and a structural support member 80 the side track 72 further includes a pair of fins 82 84 that extend inwardly from the side walls 74 76 respectively and define a gap 86 wide enough to receive the extended arm 66 configured in this way the side tracks 72 provide three separate channels the fins 82 84 and portions of the side walls 74 76 define a first channel adapted to receive the slats 64 when the shutter 62 is unrolled the end wall 78 and the structural support member 80 define a second channel that receives a nipple 88 extending downwardly from the housing 90 when the protective shutter 60 is assembled as shown in fig4 the stopping mechanism further includes a rubber stop 92 disposed within a third channel defined by the end wall 78 the fins 82 84 and the portions of the side walls 74 76 between the end wall 78 and the fins 82 84 the rubber stop 92 is frictionally engaged by the walls 74 76 78 and fins 82 84 with sufficient force to hold the stop 92 in place with the third channel against gravity and is slidable with the third channel when an additional force is exerted to reposition the stop 92 the shutter tracks 72 according to the present invention provide additional structural support for the housing 90 of the protective shutter 60 because the first channel receives the shutter 62 and the second channel receives the nipple 88 the first and second channels terminate proximate the bottom of the housing 90 conversely the third channel extends upwardly into the housing 90 and terminates proximate the top of the housing 90 arranged in.