The world famous Leeds Brick Collectors Club

[chemimike]

At a guess they might have supported filter pads on top, which could have been used to filter water, beer, vinegar or whatever

[Burmantoft Curious]

I had similar thoughts, the small holes definitely seem like some form of "drain" or sieve. My other idea was that the bricks were part of a kiln and the small holes created small focused flames (like on a gas hob on a cooker).

Thanks for replying... Really keen to find out what they are!