This one was old and tired, and though the blade was still powerful, the pivot was weak, and it could come right down. More a matter of using it after its shelf life had expired. Or they could simply choose not to be idiots. The sign helped show them their choices.
We had a professor who would leave originals in the photocopier (with its light blinking ‘paper jam’), and leave metal file drawers open right at pelvis height, and so on, but I noticed he was never absent minded in a way that might cost him a dollar. Selective that way.
