At this point I added the hardware to the lid and body of the box. I recommend getting a few extra pieces and practicing on some scrap leather to get the hang of how each type goes together.

Button studs

I chose button studs for the side closure. They come with a special tool to set them and it's pretty easy. Punch a hole the size of the shaft, push the bottom piece through, place the stud over top and using the anvil hammer to set the rivet. These are also available as a screwback, which is even easer. To set the corresponding hole in the lid you will need a hole punch the size of the stud. Punch the hole where you want the closure then using the swivel knife make a cut from the punch hole toward the top of the lid, it should look like a keyhole. Bevel the inside of the slit (make sure it went completely through) and I smoothed out the edges with the bone fid.

Grommets

Grommets set similar to the button studs, but have a hole in the center. Punch a hole in the edge of the lid that lines up with the ties you've already sewn in. It should be higher than Slid the bottom of the grommet through and place the top over it. Place it on the anvil and use the mandrel and a hammer to set the grommet. These are sold with size corresponding grommets, don't try and get away with "close enough" or they won't set right.

Treating

There are a huge variety of different ways to treat leather, this is what I prefer. I ended up with a few stains on the box from where it had sat against bare metal while it was wet. In an effort to hide these I tried a few different stains and colorings that would only slightly alter the color (or it can be dyed). For a final finish I used Fluid Film which I rubbed in and then buffed after it wouldn't soak anymore in. These should only go onto the box after it has completely dried, I made up a little wooden platform for it to dry on upside down. After dry I rubbed it with Cordovan red shoe polish which highlighted the carving on the sides but didn't do much to hide to stains. I decided, since it was a toolbox, I could live with the mistakes and went on to coat it with Fluid Film. Fluid Film is pretty hard to find in hardware stores but easily ordered off Amazon. I found it through a John Deere tractor shop locally, as it is a part they stock, so shop around. It comes in a few different varieties, I use the regular type and have used both the aerosol and the brush on (I prefer the brush on). I sprayed the inside of the box first so it had more time to soak in, then sprayed the outside. I rubbed the Fluid Film in using my hands (it's only lanolin and paraffin) and then sprayed more on until it wouldn't soak in anymore. This does turn the leather a darker color. Once I had coated the box I used a rag to wipe out any excess and then buffed the good side of the leather with a clean rag. Let this dry/soak up overnight, stash your tools in it and you're finished.

Box done!