Please consider this scenario:
Stock is at 20$. I short the 20 put (1 month to go) for 0.25 , hoping for a bullish move.
Stock goes up to 20.20 quickly, so assuming a -50 delta, the put goes to 0.15.
So I purchase the 19.50 put as a cheap insurance, for... let us say...0.05.
SO I have a bull...