She is also credited with the invention of the foot-pedal trash can, adding shelves to the inside of refrigerator doors (including the butter tray and egg keeper), and wall-light switches, all now standard. Gilbreth filed numerous patents for her designs, including one to improve the electric can opener and another for a wastewater hose for washing machines. When Gilbreth was an industrial engineer working at General Electric, she "interviewed over 4,000 women to design the proper height for stoves, sinks, and other kitchen fixtures as she worked on improving kitchen designs".