Caltech

This started as a prank played on seniors who all ditched on a specified day near the end of third-term their senior year. The underclassmen would barricade or “stack” the seniors' rooms so they could not get in. This evolved to the presentday Caltech holiday when seniors set up elaborate puzzles and activities to occupy the underclassmen on the day they ditch. At the end of the day, the underclassmen are given a bribe of candy, sweets, etc. If the underclassmen find the seniors' activities “stack” to be lame, they “counter stack” the room by barricading it. At the end of Ditch Day, the canon on the Olive Walk is fired, and the seniors become “ghosts” as the juniors officially become seniors.

This is the week-long meeting of freshmen and upperclassmen at the beginning of the school year. At the end of Rotation, the cannon is fired, and the pre-frosh (new students) become freshmen and the previous freshmen become sophomores.