What does flat gasket mean in practice?
A flat gasket fills unevenness between the pressed surfaces and requires uniform pressure around the entire circumference.
When does it matter?
Reusing a deformed seal or replacing it with an O-ring may change the joint geometry and cause leakage.
Which solutions are related to it?
The material, diameter and thickness of the joint are selected, the surfaces are cleaned and the joint is tightened without misalignment.