I had to deal with more than a couple potential catastrophes at work, by people who really should know better.
"What do you mean duct tape can't handle 4000 PSI? I used half the roll!" - customer (a hydraulic mechanic) who was wondering why the damaged hydraulic hose he brought in wasn't holding pressure and was leaking everywhere.
- or -Customer: "Oh, nobody makes these sewer cleaning nozzles anymore, so we just reuse them. The nozzles are virtually indestructible, but the female couplers they screw into haven't been made in years, so we just buy something that's close to the same size."
Me: "The female coupler is not only an eighth of an inch too big for the nozzle, it's also the wrong thread pitch, and a completely different style altogether! It ain't gonna work!"
Customer: "No problem there, we just use lots of teflon tape and sealant until it holds!"
Me: "At 3000PSI? And nobody's been killed?"
And these are the people we trust to operate and maintain heavy machinery.