Final answer:
Sealer must always be used when installing a gasket to ensure a proper seal.
Step-by-step explanation:
The statement 'Sealer must always be used when installing a gasket' is True.
A gasket is a mechanical seal that fills the space between two mating surfaces, preventing the leakage of fluids or gases. To ensure a proper seal, a sealer or gasket sealant is typically applied when installing a gasket. This sealer helps create a tight and reliable seal by filling any microscopic imperfections on the mating surfaces.