How to fill these holes…And why are they there?!

FreeBear

Section62 said: Remember that unless you use a gun-type foam you will only have a limited time (<1 hour) to use the whole contents of the can before the foam will set in the valve mechanism and delivery tube.  After that anything left in the can will be wasted.

So make sure you have all the different jobs you want to do prepared and ready to go. And make sure furniture and carpets are covered as the foam is near impossible to remove if spilt (especially important if you are moving room to room).

The tube & valve can be cleaned out with a little bit of patience after the foam has hardened. Alternatively, clean it out with a drop of acetone (nail varnish remover) before it has gone off.

If any foam does get on the carpet, clothing, or wall, do not try to remove it when wet. Leave the foam to completely harden, and it will peel off in most cases.

bpj

As to their purpose, would the location make sense for a TV wall mounted (via the plugged holes), with cables pulled through into the airing cupboard from unit below to keep them out of sight?

Apodemus

Eldi_Dos said:

To cut expanding foam flush a piece of waxed string wrapped round two bookies pencils and used as a cheese cutter should work once foam is cured,

Lol!  Love this old-time wisdom!  I suspect most of us these days have readier access to a bread-knife than either waxed string or bookies-pencils!   Ikea pencils and cable ties might be the nearest modern equivalent!   

Now, where did I put my baler twine...?