These Black Heavy Duty Steel 3-Holed Guy Line Tensioners, sold in pairs, are more suited for Hammock Suspension. However, great pieces of hardware also excel at anchoring RidgeLines, Guy Lines, etc. You can tighten lines using these with a 3:1 mechanical advantage, and once guys are tied off, they are still easy to adjust. Many uses and ideas can be found via the internet, The Ultimate Hang, YouTube, Hammock Forums, etc. 
 
The versatile 3-Holed Line Tensioners, have many uses out and about whilst not needing to remember a book full of knots.