line stretcher

例句：

1. 1.The line stretcher is used to measure the length of a string.
   拉线器用于测量绳子的长度。
2. 2. The line stretcher was used to mark the boundaries of the field.
   拉线器被用来标记田地的边界。
3. 3.The line stretcher helped me to accurately measure the width of the room.
   拉线器帮助我准确地测量了房间的宽度。