Thanks Kellyw, as you've found, it doesn't take a LOT of tools to get the job done,
I have a small foam block that I put the main tools in, helps to keep them handy
as well as I can see if one's missing and find it before it gets lost.
As far as a groove maker goes, you can do well with the end of the bone folder tool
to make a 'groove' impression along the top of the sheath, one leather maker even
uses his thumb nail while the leather is damp and rides his thumb along the edge.
He's a tricky rascal!
That sheath looks mighty good for a 4th effort! very solid looking and with the fasteners
on either end, should last a long time!
From the photo can't tell if you used glue on the sheath too? Either way one thing that
pops out would be your edges, and you can get them pretty close to even with a sharp
knife, I'd recommend drawing a line to help you keep things even.
Then use some sheets of sand paper and just drag the sheath's edge across that, keeping
the sheath up right, progressively smoother sand paper but at first something a bit coarse
to remove some leather and make the edges even.
Lastly I would then dye the edge, burnish it with a bone folder, dye it again and burnish
and then apply some Gum tragacanth and let that soak in and burnish that and then lightly
sand with 800 or higher grit.
As mentioned there are some photos and other tips in this
Thread in the leather section
which may help clear things up some.
G2