Wolf-Kim
Lovin' The Homestead
Growing up, we had a clothesline that was simply the plastic coated wire strung between 3-4 pine trees. All we had were pine trees, so we just wound the wire around a few trees and we had our clothesline.
I think some of the best clotheslines I've seen were the T-post lines with 3-4 strands and drawn tight. If you really want it to last, make sure to support the end T-posts with anchors. Usually an anchor would be a post that only came a few inches out of the ground, but was buried fairly deep. Then you would run a wire from the anchor to the T-post and make sure to put a tightener in there, that way as the years come, you can simply tighten it and not have to worry about leaning posts and sagging lines.
I think some of the best clotheslines I've seen were the T-post lines with 3-4 strands and drawn tight. If you really want it to last, make sure to support the end T-posts with anchors. Usually an anchor would be a post that only came a few inches out of the ground, but was buried fairly deep. Then you would run a wire from the anchor to the T-post and make sure to put a tightener in there, that way as the years come, you can simply tighten it and not have to worry about leaning posts and sagging lines.