Never use the bottom of a control enclosure as a shelf.
1987, before major "electrical Safety" awareness, I was troubleshooting the 4-20 milliamp control signal for an SCR-controlled 480 volt oil heater. No gloves. Reached for the meter and my hand came across 2 fuse clips at 480 volts. Never felt anything like it before. Never want to again. My hand looked like it had popcorn growing out of it where the contact took place.
Funny thing about accidents is, during the incident, you suddenly realize all at once what you did wrong.