Dave Liquorice wrote:

https://www.homebase.co.uk/chipboard...-1220-x-320-x-
18mm-3-pack_p404607

Er, so? You can clearly see the T&G that is much more than 1/4",
maybe nearer an inch on those boards, and the taper.

How do you get a 1" thick tongue on a 3/4" thick board?