Blanket policy is a policy

Policy

A policy is typically described as a principle or rule to guide decisions and achieve rational outcome. The term is not normally used to denote what is actually done, this is normally referred to as either procedure or protocol...

 which behaves similarly to a variety of things. Based on Webster's Dictionary

Webster's Dictionary

Webster's Dictionary refers to the line of dictionaries first developed by Noah Webster in the early 19th century, and also to numerous unrelated dictionaries that added Webster's name just to share his prestige. The term is a genericized trademark in the U.S.A...

 it "covers a group or class of things or properties instead of one or more things mentioned individually, as where a mortgage secures various debt

Debt

A debt is an obligation owed by one party to a second party, the creditor; usually this refers to assets granted by the creditor to the debtor, but the term can also be used metaphorically to cover moral obligations and other interactions not based on economic value.A debt is created when a...

s as a group, or subjects a group or class of different pieces of property to one general lien."