Mandolins are sharp (even the crappy ones); always use the handguard.
These are things that I know and yet I was foolish and did not always use the handguard – usually I’m half-good and just slice things carefully until it starts getting close and then use the handguard to finish up whatever I’m slicing. This evening I thought to myself “I’ll just do one more slice and then I’ll use the handguard for the rest.” And that’s how I ended up at the local Convenient Care (the walk-in clinic that’s still less urgent than a trip to the ER) with a paper towel taped around my thumb:
Don’t worry, there wasn’t really any thumb missing, just some skin. They cleaned it up and used something called Gel Foam that they use in surgeries to stop bleeding (there wasn’t enough skin to stitch back together) and wrapped it back up again and sent me on my way. In 24 hours, I can unbandage everything, give it a gentle cleanse, and bandage it back up again until I can get in for a follow-up.