How to put a zipline under tension and the proper way to attach the cable.

You'll see that a turnbuckle is not essential and in fact, it is safer without it because an element that is not on your zipline simply cannot fail.

Especially at risk are all those ziplines set up with a 1/4" cable and 1/2" turnbuckle. If you insist in using a 1/4" cable, at least do not use the turnbuckle and use the technique described in this tutorial to fine tune the tension. Be safe!