I read some where about turning off you END blocker or something. Please explain. Thanks.

It effects the first hit you do after blocking. So if your end builder is on, you will punch them for 65 damage instead of 50 damage, whereas if you leave it off, your first attack might be an uppercut for 650 damage instead of 500 damage.

If you build up uppercut, haymaker etc while still holding down block it benefits from the retaliation bonus rather than your endurance builder.