Heater box questions: reassembly.

[swamp rat]

It was just suggested to me by Frank of Franks Pick um up Parts Board vendor to buy a roll of self sticking closed cell weather stripping to do the box, I haven't looked for that yet so my interest in this thread. He also sells the round doughnut for the fan box that is exact to the original unlike most cheap Chinese imitations, he showed me both and they are way different.

Now i need to know what Gum cord is..