[rollingcabbage (OP)]

For a single ball hydraulic shuttle valve, there's a metal sphere to block one inlet port and allow oil flow from the other inlet port to the outlet port. In this case, I am referring to a cartridge shuttle valve. When I shake it, I can feel the ball rolling up and down. Therefore, I am wondering if the ball is subjected to gravity if I installed it in a different orientation? And how does it actually stay in place.

[alancalverd]

The ball doesn't stay in place unless there is a pressure imbalance between X and Y. The object is to allow flow  from the higher pressure source X/Y to the outlet A without backflow into the other source.