a double edge sword is simply sword with two sharp sides, often it was used on broad swords, it is often believed of by people that broad swords are these long, straight swords, that look something like this
but that actually qualifies as a double edge sword
no example needed, the definition is self explanitory
the proverbial "Catch-22" where one is damned if one does, and one is damned if one doesn't.
"Corporate lay-offs are a double-edged sword. The company saves money by not having as many salaried people on board, but has to pay more overtime wages to the fewer people that are left so the work can be done by deadline."
Proverb used to convince one of not using a weapon (literal or figuritive) because it may come back and hurt yourself. Rather useless especially with the fact that one can learn how to use a double edge sword (literal or figuritive) effectively.
George: single edge sword is better to use cuz it wont cut you
Bob: A skilled swordsman can use any sword.
Jill: Anger is a double edge sword, it hurts you as well.
Jack: I've been using anger for 8 years and I haven't changed a bit.