Author: Joe Talmadge

Last Updated: May 1998

What is a Blood Groove For?

This question comes up every 8 months or so. The blood groove on a knife probably is derived from the channel present on swords, where it is called a "fuller". There are some persistent myths floating around about the function of blood grooves, from "releases the vacuum when the knife is thrust into a person" to "no functional use, purely decorative". Let's talk about these wrong answers first, before we talk about the right answers.

Wrong Answer #1: Releasing the Body Suction

Basically, this theory postulates that the blood groove is present to facilitate withdrawing the knife from a person/animal. In this scenario, it is said that the animal's muscles contract around the knife blade, and that this causes a vacuum, which makes the knife difficult to withdraw. But on a knife with a blood groove, blood runs through the blood groove and breaks the suction, so the knife can be withdrawn with less difficulty.

One problem is that there's no evidence that this suction ever really happens. Also, over and over again people report that there is no difference whatsoever in the difficulty of withdrawing a knife with a blood groove vs. one without. This is one theory that has been tested and found wanting.

Yes, I realize you may have heard this myth from your deadly knife instructor, or read it in a book somewhere. But the experts agree that it is false. If your knife can cut its way in, it can just as easily cut its way out, with or without a blood groove.

And with that, I am going to change terminology from "blood groove" to "fuller", since we all now know the so-called "blood groove" is not playing a blood-channeling function.

Wrong Answer #2: Purely Decorative

There is a grain of truth to this one. Although a fuller does play a functional role, on a short knife the effect might be so small as to be insignificant. Many believe the fuller plays a strictly decorative role on knives or swords under 2