In article 7a9bb77a-81c2-4c8c-8d8b-
, says...
I have always found expanding foam really messy and difficult to
control, which is why I was not so keen to use it, so any tips
gratefully received.


Put plenty of newspaper down. Flatten the end of the delivery pipe and
make sure it reaches well into the slot before you start. Close one side
of the gap if open (masking tape) and then fill as deep into the slot as
you can.

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Skipweasel - never knowingly understood.