InterpretationU.K.
20. In this Part the following expressions have the following meanings respectively—
“locked” means secured by a device which prevents unauthorised operation;
“restricted visibility” means any condition in which visibility is restricted by fog, mist, snow, rainstorms, sandstorms or any other similar causes;
“a closing appliance” shall be deemed to be below the margin line if the sill of the opening with which it is associated is below that line.