Ladder yarn or train tracks yarn is a type of

novelty yarn Novelty yarns include a wide variety of yarns made with unusual features, structure or fiber composition such as slubs, inclusions, metallic or synthetic fibers, laddering and varying thickness introduced during production. Some linens, wools to ...

. It is constructed like

ladder A ladder is a vertical or inclined set of rungs or steps used for climbing or descending. There are two types: rigid ladders that are self-supporting or that may be leaned against a vertical surface such as a wall, and rollable ladders, such a ...

s, with a horizontal stripe of material suspended between two thinner threads, alternating with gaps. Sometimes a contrasting strand is fed through the gaps to produce another look.

References

Yarn {{textile-arts-stub