way back when i worked at a small family-owned boat dealership ( i was the only one not related) i rigged the chair and desk in the small office, it was a 10 x 10 office with glass frontage, and every morning the routine was the same, the secretary would walk in, set her coffie down, pull out the chair and sit down. i had took about 7-10 of those "pull" firecrackers (had a string on each end) tied one set of strings to the desk leg and the other ends got tied to the chair leg. i took up a spot where i could watch and sure enough, glad she sat the coffie down. there was a stream of expectives, followed by my name. i was laughing so hard i couldnt play dumb. when i asked how it was known it was me, i was told the others (all related ,remember) wouldnt have dared. its still funny , even after 15 years.