I knew architrave but not astragal (which sounds rather nautical, I think), so thankyou for that one. I must have learnt some new words recently but I can't think of them, which is rather sad.

When I was writing software for breweries I learnt 'ullage', which sounds like it ought to be a mediaeval tax but in fact means 'beer which ends up not being sold to a customer' - usually used more specifically as 'some of an opened barrel of beer which a landlord has sent back because it seems to have gone off before its sell-by date and which we therefore need to test to see if we really do need to provide a refund'.