Blocking of inheritance is a powerful capability, and very useful for specialized users or systems. Useful, that is, until it causes you problems. Then it quickly becomes a nuisance. When you find yourself staring at GPO settings that you just cannot seem to get to apply to a particular computer, navigate your way up the OU structure from where that computer resides up to the very top of the domain, watching out for those little blue exclamation marks along the way. If Block Inheritance is enabled on an OU that is four tiers up from where your computer resides, that block is still affecting your computer! Take a look at the following screenshot. If my laptop was sitting inside the highlighted OU called Dell, even though that OU is way down the chain away from IT Department, my laptop would still be blocked from inheriting GPO settings because I have Block Inheritance configured on that IT Department OU. This block affects everything nested inside of it: