Alloy 3-Holed Guy Line Tensioners (sold in fours) are great pieces of hardware that excel when anchoring ridgelines, guy lines etc. You can tighten lines using these with a 3:1 mechanical advantage and once lines are tied off they are still easy to adjust. 
 
It is recommended that these are NOT used for suspending your hammock. We also sell a Heavy Duty Steel version better rated for Hammock Suspension.