What insulation material between PCB and chassis?

Hi guys,

What type of insulation material do people use between a PCB and a metal chassis.
I know stand offs are used as a spacer underneath offering protection, but what can be used on top or below, as I often see in commercial products a type of hard card.
The reason for asking is my current project fits very tightly into its chassis.
Thanks in advance.
 
As an alternative which *might* be easier/faster to source, old style insulating paper, generic name "Presspahn", the typical brown insulating paper you see in millions of transformers.

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If you know a transformer or motor rewinder nearby he should certainly be able to spare some, he might also have Nomex or Mylar.

Absolute worst case, and in a real hurry, many stationery shops carry Presspahn/"fiber" folders you can cut to size with standard scissors.

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