[pavel_lishin]

I know exactly how I would defend myself with an umbrella against someone who has a knife, and definitely wants to stick me with it [†].

If my umbrella is already opened: throw umbrella at them, and run.

If my umbrella is still closed: throw umbrella at them, and run.

[†] If they're just threatening me and asking for my wallet, I give them my wallet and ask if they would also care for an umbrella.