Steak & Onion Sub.

We popped into a furniture emporium to buy some curtain fixtures; we did eventually find them, but not until after a helpful sales-person had told us they didn’t sell them. We stayed long enough to have some lunch where we pondered on the nature of “steak and onion sub” before crossing the carpark to the DIY place where they had suitable fittings at twice the quality and half the price.
 
It turns out that a “sub” is a style of bap – if you’ll pardon the ambiguity.