What is the bolster in a knife?
From the dictionary: a part of a tool providing structural support. To support or strengthen; prop up.
The bolster, commonly found in high quality kitchen cutlery, is the thick piece of metal that extends from the handle into the blade about a 1/2”. It provides some protection for your fingers as well as balances the weight of the knife. They are more common on high quality commercial knives as it shows the knife is originally made from one thick piece of steel as opposed to being stamped out. The bolster is not to be confused with the knife guard, which extends outward from the knife and handle instead of flowing between them.