Having spent 30yrs in IT / databases and business apps I naturally think about the world in terms of 'how I would record things using codes'. It occurs to me that I probably organise things and my possessions in a way most people do not. In schools with the advent of colour printing many reports are now RAG coded Red, Amber, Green (traffic light coding) generally meaning Bad, OK, Good. Books are often coded using colours or short alphanumeric codes to indicate Year group, difficulty or scheme etc. Expensive equipment that schools need to report on inventories for their asset value are often coded or you can buy pre-coded labels suitable for PAT testing IDs ( Portable Appliance testing - a statutory requirement for all mains plugs/wires/adapters/PCs/ printers/ tools). Do you have any coding systems you would like to share or have a cataloguing problem you have not found a workable solution for ? At home I wrap coloured insulating tape bands around both ends of electric wires: red = Do Not unplug, Yellow for lights, Blue for Device, Green for unplug at will and optional white band/s to differentiate when deciding what I am unplugging from the proverbial 'rats nest'. At work, IBM had a wire coding system where every wire had a unique code printed on at at 1metre intervals so that network engineers could identify every wire in every communications cabinet. Advice for anyone designing databases: Do not use Postcodes as a primary key because they are not unique and do change when the GPO rearranges sorting offices.