Abstract: A light-weight, liquid-blocking ring assembly for a surface drain for preventing a harmful liquid spilled nearby from entering the drain, which can be quickly and easily installed by a single person, and includes positive verification that none of the undesired liquid has entered the drain. The assembly includes (1) a center portion having a latching mechanism for attaching and drawing the assembly towards the drain, (2) a peripheral band which surrounds and is spaced from the drain, and which carries at its bottom edge a resilient gasket conformable to the surface surrounding the drain, and (3) an intermediate structure connecting the center portion and the peripheral band without blocking a clear view of the entire surface surrounding the drain.