If you've ever thought, "Gee, these towers would be a lot easier to align if I had several more arms," this is for you! Once installed, it will pull the towers as close to the center of the bed as possible. Friction keeps the towers from moving up or down, and will greatly reduce the tendency of each tower to "walk" as you torque down the T-slot nuts.
I got the original idea from someone else on the SeeMeCNC forums. I forgot his name. (If that was you, let me know and I'll credit you here.)
I have a backburner project to adapt these clamps so that the threaded rods sit completely outside the build volume, so they can be left mounted permanently. This is not just good for keeping it aligned - it will also make the structure MUCH stiffer, which is good if you want to do some serious high-speed printing. Other projects are a higher priority for me right now, but if some people ask I'll set aside some time to finish the permanent clamps.