(espionage) the barrier between compartmentalized intelligence information and those without access to it, especially military personnel who might need it

present participle of barn door

(historical) A door with a baize surface attached to deaden noise, traditionally separating the servants' quarters from the main part of a house.

plural of baize door

To ask for entrance or admission into. / Used other than figuratively or idiomatically: see knock, on, the, door, of.

(bingo) four

simple past tense and past participle of knock on the door of

present participle of knock at the door of

Third-person singular simple present indicative form of knock on the door of

simple past tense and past participle of knock at the door of