WAslayer
Honorary Master
If it's a union lever lock, I will fully believe it's not been changed in 40 years.. those things are absolute bullet proof locks.. that's also why you pay 500bucks for them..Weird euphemism but I will roll with it. It's caused by menopause and you could use some KY.
In seriousness though I would start by inspecting the key, does it look like it could be worn or broken in any small way? Do you perhaps have a spare or notice any difference between different keys for the same lock?
Yes WD40 isn't the best thing to use, you should just change the lock, hard to believe it hasn't been changed in 40 years.
Is the issue with putting the key in or turning the lock? What kind of lock?










