Sounds out of this world from the fourth dimension, doesn’t it?
In many circles, this tool is also called the Cable Stretcher but “4th Hand Tool” is its more common moniker. This tool handily pulls the cables for the derailleurs (the shifters) and brakes in order to free up a hand of your own to tighten nuts and bolts. As one reviewer on Amazon writes, “When your bro’s paw is wrapped around a cold one and you need another hand…,” essentially this tool gives you the extra hand you need when you need to tighten a cable. I especially find that this tool offers me the strength that my simple tug won’t deliver to make my brake tension that much more responsive.
While the handle is loose, slide the cable through the grooves at the top with the flattened arm butted against the brake or derailleur (the part that shift your chain). When you clamp the handles, the tool grabs the cable and pushes off the brake or derailleur, pulling the cable taut. While one hand holds that tool, the other is then free to tighten the nuts or bolts to lock the cable down. There is a handy little video where you can see the clamping and pulling action of the tool on eHow.