I made a corner clamp out of a couple of squares, some epoxy and a few screws. The idea here was to have something that I can use to clamp 90 degree angles with. I looked in to buying the 3D corner clamps but they were $30-$35 a pair. So instead I came up with this idea. The squares were $2.00 each. The epoxy and screws I already had in my garage. They are nowhere near as good as an actual 3D corner clamp but they seem to do the trick.
I got this tip from watching other Youtubers. When ever I'm mixing a small amount of epoxy I put down some blue tape to mix on. This way I know the surface is clean and when I'm done I can just throw away the tape.
The first picture is how they will be glued together. You spread the epoxy on to one of the squares nice and thick since there are a lot of crevices on the squares. Then you put them together and use some spring clamps to keep them nice and snug. You will most likely have some squeeze out now would be a good time to clean it with some paper towels. You let it dry for how ever long the instructions on the epoxy say to leave it drying.
Next I cut out a notch to create a hold or grabbing point for the clamps. I used an angle grinder with a cut off wheel but you could use a hack saw since these are aluminum which it isn't to tough to cut by hand.
And this is how I use it. Basically this allows me to join two pieces of wood at a 90 degree angle. The clamps hold the two pieces while I pre-drill and then screw together the wood. It worked pretty well once it was clamped I could lift the whole piece up and move it around and didn't have to worry about losing my 90 degree angle.
I thought it might be a good idea to reinforce the epoxy with some screws. I figured that over time and with use the epoxy wouldn't hold. So I drilled three holes, one on each corner and then secured them with a fastener and a nut. The holes I drilled for the screws were very close to the diameter of the fasteners I used so that there wouldn't be any wiggle room.
The beauty shots. ;) Here is what the finished product looks like. I hope you find this helpful and maybe add it to your tool collection. I bought the corner clamps at Harbor Freight for $1.99 each. This is a relatively inexpensive solution for about $5 I was able to make this corner clamp.