Roofing

I have read recently about roofing and brickwork, but cannot now find the
article, and wonder if anyone can help. From memory it is in paste form
which you put on about 1/8th inch thick, and then apply a template when
still wet in the brickwork or roofing pattern.
From this vague description is anyone able to tell me the name of company
which supplies this material in the UK.
I think the article/advert was in the Dolls House and Miniature Scene.

TIA

John