The purpose of the investigation was to examine and contrast the patterns of fracture and deformation of cubical box-like structures open on one side, when impulsively loaded. Part 1: Brittle cubical boxes of plaster of Paris, open on one side, were subjected to intense impulsive point loading. The resulting terminal fracture patterns are shown and discussed. Part 2: A small number of thin metal boxes were point loaded by the impact of a heavy slow moving mass. The resulting plastic deformation patterns are described and discussed. In the Appendix, energy absorption due to bending is estimated and related to the results of Part 2.