Very handy to have if you make many strings--not sure that wood will hold up over time though. Mine is made from square tubing, and I'm on my second one--first one broke (fixed it), then bent to the point I couldn't adjust it for length. Second (and third--have a back-up now) has heavier gauge steel.
One thing you'll want to watch for, especially with dacron--let the tension off and wait a minute or so before taking a final measurement. If you put a lot of tension on, strings will stretch--dacron will stretch a lot--then draw back up some when the tension is let off. A 7" screw hook will give you more room to stretch with vs. the turnbuckle.
They are also great for serving strings and tying in silencers.
Chad