Nắp ắc quy

A cover is a panel or cap that closes off a housing or opening to protect the parts inside.

It keeps dirt, water, and debris out and contained fluids in, and provides access for service when removed; some covers also locate a seal or gasket at their edge.

Covers are used on the engine, gearbox, and many housings across the vehicle. The correct cover matches the housing and any sealing surface it carries.