I think the 'notch' is this bit (circled) looks like its bent in the photo, but it's actually a curved 'indent' which I reckon is what the hook should register into...
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Agree with RedFish, the peel-and-stick foam is a waste of time, I cut these out of some foam packaging material, they work perfectly...
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And a few reinforcements along the way as well...
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Fits perfect... Dont forget the four bolts on the blower/fan motor do most of the holding, the j-bolt is to be tightened just enough to make the seal against the plenum 'breeze-tight'...
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