If you'd prefer to watch a quick video explaining exactly what the Trellis is and how to use it, you can take a look at one here:
If you prefer to read, I'll use this introduction to quickly describe what the Trellis is. Essentially it's a modular blacksmithing jig based on a regular grid. It's been designed to be easy to build and use (especially in makerspaces or hackspaces), and also to make blacksmithing projects simple to share with other people over the internet.
The Trellis itself consists of four main parts: A baseplate, a frame, and two rulers. The frame and the rulers are used to make dimples on the baseplate at points corresponding to the grid. Those dimples are then drilled out, and pegs are placed into the holes and disks of various sizes are sometimes placed onto the pegs. Then you heat up a piece of steel rod in a forge and bend it around the pegs and disks to create a forged piece of steel. The piece can range from a simple one-off ornament to dozens of pieces of almost-identical hardware to a component in a machine. And, once you've completed your piece, you can rearrange the disks and pegs to create a wholly different item.
Cool, right? The best part is that if you come up with a piece of your own you can share the coordinates for making it with other people - "...put in a peg at X, put in an 8cm disk at so-and-so, and begin by wrapping the taper of your rod around the peg at such and such."
But before you do any of that, you need a Trellis. So here's how you make one.
Step 1: Step One: Cut Out Your Trellis and Mark It With Its Co-ordinates
To begin, send the Trellis_CNCfiles to a CNC cutter, and give them a piece of 78cm x 45cm 1/2" plywood to cut them out of. The .jpg file included here shows the dimensions that need to be cut into the piece, so maybe send that their way as well.
After getting your plywood cut but before chiseling it out of the frame you can also use the Trellis_LaserCutter_Files files to laser cut your numbers into the wood, but you could also draw them on with a pen or sharpie if you liked. Either way, make sure that you put the letters and numbers into the side of the plywood sheet that has remained totally flat rather than the one that the CNC has routed low areas into. Once this has been done, remove your Trellis from the sheet of plywood and clean it up until it fits together nicely.
You may also want to reduce the thickness of the rulers, but that's optional. There are many ways of doing this, but personally I used a bandsaw.
Step 2: Step Two: Create the Baseplate
For this step you'll need a 30cm x 30cm piece of 10 gage sheet steel and four screws which are short enough to not penetrate all the way through both the steel sheet and the wooden base, but are long enough to make sure that it is secure. 1.5cm is a good length to go with, but use whatever is handy.
Use a centrepunch to mark out dimples in the corners of the sheet of steel (these holes don't need to be exactly placed, they're just there to fix the baseplate together). Then drill those dimples out with a drill bit that corresponds to the size of screw you're using. Countersink the holes if you want the screws to lie totally flat.
Next, use a drill bit that's a little thinner than your screws to drill out pilot holes in the four corners of the wooden base. Now you can screw the baseplate together.
Step 3: Step 3: Filing Down the Edges
Now you've got a baseplate, but because the corners of the metal sheet are sharp your frame probably won't fit onto it. You can fix this in about then minutes using a file.
Fix your baseplate down securely using clamps, a vise, or whatever's handy. Then file down the corners of the metal sheet until they're flush with the wooden baseplate below. You'll know that you're done when the frame fits onto the baseplate without any fuss.
Step 4: Step 4: Prepare the Rulers
Finally, you need to push a couple of metal pins into the holes on the ends of the rulers. These will let your fix the rulers onto the frame.
To make the pins cut four sections of 3/8ths round rod to about an inch and a half in length. You shouldn't really need to force them into the rulers, although the fit will be snug. If you're really needing to push to get them inside I recommend making the rod just a hair thinner with a file or some sandpaper.
Once you get this finished, you're done! Check out this Instructable for a good first project - https://www.instructables.com/id/The-Trellis-Project-Forging-a-Hook/