Household Essentials' aluminum clothesline tightener helps tighten a sagging clothesline and fight the inevitable effects of gravity on your lines by fixing this tightener to them. The tightener draws the line in, tightening it without forcing you to restring. Use it with fixed line or pulley systems and never mess with burdensome knots again and thread your line through the spring-loaded center and pull the clothesline to tighten. 3 ball bearings grip your line keeping it taut and the spring action center prevents it from slipping..