I always saw them as a waste of time, but a faulty gauge almost had me replacing the wrong part. Now I test my tools first thing every morning, why wouldn't you?
Yeah, learned that with a pipe wrench where the handle just... spun freely. Sent me for a loop before I even started. Now I give it a wiggle, saves the embarrassment.
Ever had a tool fail mid-job? I learned the hard way when my calipers were off, almost costing me a whole batch of parts (talk about a wake-up call). Now a quick function test is part of my setup, no excuses.
Tools failing like that can really mess up your day, can't they? After my tape snapped, I began testing it on a known distance before each use. That simple check saves so much time and frustration later.