Learned about "Shape Coding" from Ian Levy's "goodbye to the GHCQ" post (https://www.ncsc.gov.uk/blog-post/so-long-thanks-for-all-the-bits) today (in section 1 of said post, the bit about B17 cockpits in WWII).

Question: What real-world control around you would you change the shape of to make it more discernable?