Review on Enhance Precision and Efficiency with Adjustable Clamp 9133 Corner Splicing by Elmito Yeager

You'll need a protractor to set right angles, but these clamps hold boards together securely so they can be nailed, screwed, or glued. I use 2 of these on each end of 12.5" boards and it all comes together perfectly. The pony is no longer manufactured so they may not be available. So if you need 1 or 2 of these, buy them now. The only other adjustable clamps I could find cost over $700.