These corner blocks turn an ordinary ratcheting tie down strap into a four corner band clamp. They are used to clamp boxes while gluing them together. The blocks are designed for 1" wide straps such as these from Amazon.com:
Thread the strap through the blocks.
I printed my blocks in PLA with 5 perimeters, 7 top and bottom layers, and 20% infill. Using ABS would make them even stronger. You can also use the more standard 3 perimeter and 5 layer top and bottom and increase the infill to around 50%.
I included photos of my box project for which I designed this clamping system. These clamps work well with boxes with mitered corners. The clamp tends to pull the corner miters into alignment.