The early chapters in this book described the mechanisms of human gait, including discussion of falls in different circumstances. It was explained that walking is a complex feat of biological engineering, involving postures that are inherently unstable. Separate attention was given to our visual sense, in view of the significance of this for both monitoring the environment and maintaining balance. Processes involved in slipping and tripping have been described, together with an account of the interaction between footwear and flooring and the manner in which this is affected by the presence of substances such as liquids and ice.