If I block I immediately stop. It's important to be my own speech cop. Getting stuck just reinforces stuttering habits, so it's vital to not suffer from any stuttering attacks. I will (1) stop, relax and rewind, then I can continue on. (2) use a vowel before the blocked syllable - for example, if I block before the word "break", I will add an ah- sound before it. Or (3), I will drop the first letter of the word all together, so "break" becomes "rake". Anybody who knows the English language will know what I'm talking about.