I often use wire instead of twine to tie things because you can get it pretty tight without fancy knots.To tighten it you lock the wire into place by bending it around another wire. You pull and bend. When you make a band or a clamp, pulling and bending results in the whole thing sliding and turning backward and sapping your tension. This gizmo gives you a groove to push with and notches to pull with so when you bend the wire over it holds the tension. It can get remarkable tight.
I was at PrepperCon and I saw a man selling a survival tool that makes clamps. It was essentially a piece of sheet metal folded over with a clock key through a hole in the side. It was called the Stronghold Haywire Klamper. He could make strong clamps with only wire which he also sold. I was impressed but didn't buy one. When I got home I wanted it so I got on-line but couldn't remember the name! So I started searching. What I found was Instructables by GeeDeeKay andTechnomancer07 who built clamp forming tools of a very different design that take a fair bit of skill to make. These use a threaded puller in a tube, which if professionally made, cost as much as 100 bucks! To make my own I wondered how I could use "found" items to make a clamp forming tool without all that artful cutting and grinding. I got out my sketch pad and scrawled down a few designs and looked at some old patents for ideas. I was able to make the "fancy" tool from a turnbuckle and some odd hardware. It worked pretty good and it had some advantages over the original. I have included a picture of it and doodled on it how the wire is wrapped around the tool and the work to form a clamp. Other "found" items I considered were a bicycle brake, threads mounted on pliers and a caulking gun mod.
The caulking gun mod was so much easier for me to make that I got excited and wanted to tell the world. To make it you'll need a caulking gun with a functioning hand lever, an angle grinder with a metal cutting disk and a vice.
First I cut of the end of the caulking gun while it was held firmly in the vice. I had the plunger all the way in so I could cut off the plungers disk at the same time as I cut the end off.
Then with the plunger still all the way in I used the mighty force of my bench vice to crush the tube of the caulking gun mostly flat. Mine bent a little upward. Working the vice, repositioning and squeezing with the object of having two flattish parallel sides.
Now pull the plunger all the way back. I didn't have to free it from the sides because I didn't crush it super hard in the previous step. There was a tight spot but it got cut off later.
Next cut off the excess length. I cut mine were the crushed in sides were nice and parallel and intersected the passing of the plunging rod. Once crushed the tube bent upward as it flattened, so the length is arbitrary. Locating a spot to place "tie off notches" is the primary consideration. The tool will push and pull so it needs a place to anchor the wire your tightening and you'll need to leave enough metal to make these notches. I took off a little more than half of the original tool.
Half an inch to an inch-ish from the end you cuff off, cut two 45 degree notches in the parallel sides of the tool. When you use the tool this is where you will anchor your wires to tighten them.
Finally use the grinder to cut a shallow notch in the end of the plunger rod. It needs to be deep enough to catch a wire without slipping off and no more. If the groove is too deep the tool may bury itself in the work and scratch it. You might prefer hand filling or a hacksaw for accuracy but a cutting disk is faster. The groove is cut on the horizontal: If the trigger handle of the caulking gun was north south you're cutting your groove east to west. You want just the groove to reach the wire not the sides of the rod, so taper the rod down to the tip parallel to the sides of the groove. When you've pulled the wire of your clamp tight, you'll have to fold over the wires to lock them in place without marring the surface of the work. If the sides of the groove are too thick they will dig in. So the sides of the groove must come close to the sides of the rod. The length of the groove depends on how wide you want your clamps. My plunger rod is 3/8" wide so that is the maximum width of clamp I can make. However in forming clamps, narrow clamps are easier to prepare so an 1/8" of an inch might be a good starting point. The advantage of using a caulking gun is that it has a lot of travel so you can afford to grind off a tip you don't like and tweak it to what works with the wire you have. I happen to like concrete tying wire because I've got lots of it. I also have some galvanized wire but I have been advised that "safety wire" is the best. Oh well. I think some thick copper wire would look good banding some things together but then I would need to resize the end of my tool to match its diameter.
At this point you might be wondering how do I use this thing? I've put some annotations and doodles on the drawing to give you an idea. The instructable by GeeDeeKay called Hose Clamp Magic has some tips on wire and how to form a clamp.