A method of knife carry that became popular in World War II and has continued off and on to the modern day is the wearing of the knife on a pistol holster. The practice originated with the more specialized units such as parachutists and Marine Raiders but spread out to the regular ranks as time went on. First practiced with the M1918/MkI Trench Knife and then later types like the Kabar and M3. The reasoning behind it? Mostly to free up space on the belt (or also condense the amount of things hanging from it) or be able to have the knife at an easy right hand draw position like the pistol.
Notice the small tabs on the sheath for attaching
The M1918 Trench knife is visible behind the holster in this 1943 photo
How to do it
Now there are essentially two ways to mount a knife in an M1916 scabbard. The first is to just take the knife and slide it behind the belt loop section of the holster. This is the simplest way but as you can probably guess not the most ideal as it leaves the blade exposed.
Technically functional but not recommended
The other method, and as far as I can tell from photos more common, is to slide the sheath behind the loops. This is easiest with the early sheet metal sheaths of the M1918/MkI. And I speculate that is a large factor in the birth of this trend. The WWI vintage scabbard attached to belts with two small metal tabs. Tabs that were easy to break off. So mounting it in the holster is a much more secure way to carry the knife. The later M6 and M8 scabbards are a tighter fit but work just fine. Plus they have the added benefit of being able to secure the tip to the holster.
Now to do this with a Kabar you will have to pop/cut the couple stitches on the holster to make it fit.
The tip of the knife is pointing to the stitch to pop/cut.
Some examples in use
I’ve seen this done on modern drop leg or thigh rig set ups during the early-mid GWOT but the only pictures I could find nice (without spending hours digging) were cringy ones of tactical Tommys in their living rooms showing off their Serpas so I’ll have to skip the modern incantation.
As far as the amount of use this method saw it wasn’t particularly widespread. So while it does show up in almost every corner of Army and Marines it was fairly uncommon. The highest percentage it shows up is with the early paratroopers who were all issued sidearms regardless of rank as well as the old M1918 trench knives. So you have tons of holsters and knives with shoddy sheaths needing to be carried along with all the other gear. It’s similar to the shoulder holster or knife on the suspenders. Yes it was done but was typically uncommon outside of certain units.
I am a big fan of the M1916 holster, For how old of a design it is, it is a really natural holster to use. Sits at a comfortable height, has good retention and is reasonably fast to draw from. Plus you can do the whole trench/fighting knife behind it. I think it is a design ripe for an update, cut for modern sidearms and maybe out of Cordura and with MOLLE adapters. Tried to pitch the idea to Tactical Taylor back in 2015 so they could release it as the M2016 holster but I don’t think they quite understood what I was explaining.