What is this?

[Hassan Huq]

Recenlty moved into a house and discovered a leak from one of the bathrooms upstairs. I cut into the ceiling and I think I’ve discovered the source. What is this?

In the picture, the tub and supply pipes leading to the tub are behind me.

Thank you in advance.

 

[Mr_David]

That is the inside the side skirt of a fiberglass tub.
The triangle is a bracket that is connected to bottom of tub and to the inside bottom edge of the tub skirt.
some tubs ( steel ) have an angled cross brace to back up the bottom corner.




Fiber glass tubs sometimes have that bottom brace