Pandemic-induced cleaning aside, when it comes to doorknobs, I am not like most people. As a curator interested in the functional designs of everyday life, I am fascinated by the combined ubiquity and invisibility of doorknobs. Take a quick count: how many doorknobs are in your residence? Or, imagine a typical day before social distancing. How many thresholds would you pass through as you navigate home, transit, school, work, coffee, lunch, errands, and social and cultural engagements? Picture the doors in your mind. Which ones have knobs, levers, push plates, or handles? What are their shapes, colors, materials, and textures? If you have trouble recalling, you are not alone. Most doors offer such seamless interactions that they fail to register in the conscious mind.
Door hardware also provides curious and instructive examples of mechanical principles. The most familiar doorknobs today (external link), lever locks, feature a rotating knob which disengages a hidden latch. The knob turns an internal spindle and cams, translating rotational motion into linear motion and sliding the latch. Imbedded springs ensure that everything returns to its original position when we let go.