Whether you’re cleaning your kitchen after a big meal or finishing a painting project, it can be tempting to pour just about anything liquid—or sometimes even solids—down the drain.

Typically, we’ll throw a simple helical spring lock washer on a stud or bolt, torque down the nut nice and snug, and call it a day, feeling like we’ve made a secure joint. But nothing could ...

The mystery of the lock nut, though, isn’t how it works. The nylon insert is just a little too small for the bolt, and the bolt, being harder than nylon, taps a very close-fitting hole in the ...