Well the toothpick shifts to one side as you put the screw in.

The problem with a stripped hole is that the hole is now as wide as the screw, so the screw has nothing to grip anymore. Conventional wisdom in this case is that you should get a wider screw and try again, but that’s not always something you have on hand, especially when travelling.

But the toothpick hack takes it the other way. It’s effectively narrowing the hole again by taking up space in it, and now your same screw can work again.