My memory of the under-stairs shops are the small businesses in the small corner on the ground floor of the tenement buildings.
I have lived near Wing Kwong Street in To Kwa Wan for decades. Choi Kee Department Store, which is now closed, was the under-stairs shop which I always visited.
My mother always used sandalwood soap for bathing, as she liked the scent of the soap. Since the large supermarkets did not sell such soap, so she had to buy it at our familiar Choi Kee. The shop was so convenient, genuine and friendly, but now, it is closed and we all miss it. The people in the small under-stairs shops, working hard to earn their living for their families, deserve our admiration.
Nowadays, new buildings are everywhere. I believe that the under-stairs shops will all be replaced in the near future and will be buried in history.