When building a carport or other structure that requires square walls or sides string line is used to ensure your work is square along any dimension.
1. The four corners of your carport structure are erected as per the particular instructions for the style you have chosen. Nail one end of the string line into the end of post No. 1.
2. One end of the string line is tied at the top to the exposed portion of the nail, beneath the head. The string line should be pulled taught and attached to the post opposite the post with the string line already nailed to it.
3. The string line should be removed from both posts. The string line is attached in the same manner to the two opposing posts that have not yet been attached to the string line. Align the four posts properly and square, then string line should be attached to the two new posts with the same tension in the string line of the first two posts measured.
4. The previous three steps are repeated to measure for vertical square measurement for each carport side. The string line should be mounted from the bottom of one post to the top of an opposite post along one side wall.
5. This string line measuring process is to be repeated for all four sides of the carport.