SplinterGroup ..... Not sure what the two thingies to the rear are for
The two thingies at the back... you should have 2 of the left thingies... The right thingie can be combined with one of the left thingies, to hold a piece much like you would in a lathe between a dead centre at one end,
and the other left thingie mounted on the clamp as the other dead centre.... you now have a manually operated lathe... all the hand toolies will think you're a hero.
The right thingie can be used as a "dog" so you can have a "tail vise" in the middle of your bench.
Just watch those left thingies as they have sharp edges that can leave ring imprints on your work, much like, but bigger than a live/dead centre if you use too much pressure.
PS. You need to do an about (360°/2) turn with your mounting clamps.
If your first cut is too short... Take the second cut from the longer end... LBD