Rod seals are employed in what situations? One of the most important seals on any sort of fluid power equipment is the rod seal. The rod seal keeps the cylinder's pressurized hydraulic fluid from leaking. Leakage can cause equipment failure, system failure, and environmental/safety hazards. Rod seals are also defined as a type of dynamic seal, which is positioned inside the cylinder head. These are squeezed against the cylinder's rod, confining the fluid and allowing pressure to be created.