Casting back to Mr. Lunt's eighth-grade grammar class, a person would LIE down, but he/she would LAY an object down. (I LIE on the bed, but I LAY a book on the bed.) In this situation, "lie" is an intransitive verb (has no object), while "lay" is transitive (must act upon an object). ("Lay" CAN be transitive, but only if you have the ability to produce eggs....but let's not get into that.) As your sentence is an imperative command (with an implied "you" as the subject), in which a person (you) is acting upon an object (the crate), I would say LAY FLAT TO UNPACK. Mr. Lunt would be proud. :) Nickie __________ Nicole M. Bouvier Scheduling & Exhibitor Relations Director Smithsonian Institution Traveling Exhibition Service (SITES) <[log in to unmask]> 202.357.3168 x120 phone 202.357.4324 fax