A wood working clamp used in a set of 4 to mount a glue up to keep edges plumb. The 90 degree angle in 4 brackets working together allows for equal pressure to be spread across each of the corners.

These are intended to be used with tie down straps. The clamps can be resized but they are designed to work with tie down straps that are 25mm in width.

I suggest using this with a racketing strap which you can find at your local hardware store.