I used the same rivets and washers that I used to attach the base to the cake pan. See pictures with directions below.
The arrow points to the channel in the gasket I used to place the washer and rivet.
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This is looking at the outside of the gasket as it is attached to the outside of the cake pan, you can see the rivet and gasket. I pushed the gasket up against the lip in the pan and measured the distance that I need to drill the holes in the pan so the gasket would fit tight against the lip. Place the rivets every 4 to 6 inches.
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This is a picture looking at the inside of the pan. You can see the lip on the pan and the end of the rivet just to the left of my thumb.
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Another picture looking from the outside of the pan and how the gasket hides the rivet. I painted mine black after I had everything installed to hide the white rivet and washer.
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Here's the rivets and washers I used.
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