a base unit;

a middle unit coupled to the base unit;

a rotating unit positioned between the base unit and the middle unit, wherein the rotating unit is configured and disposed to be rotatable with respect to the base unit, wherein the rotating unit comprises a first engaging portion formed thereon and a first wing part and a second wing part, and wherein the first wing part and the second wing part comprise a space therebetween for winding a string; and

a cover unit coupled to the middle unit, wherein the cover unit comprises a second engaging portion inserted into or separated from the first engaging portion;

wherein the middle unit comprises a responsive protrusion,

wherein the cover unit comprises a ratchet protrusion for limiting rotation in one direction in response to the responsive protrusion,

wherein the responsive protrusion and the ratchet protrusion are arranged in a direction parallel to the rotation axis of the cover unit and engaged with each other,

wherein the responsive protrusion is disposed on an upper surface of a partition extending from a side surface of the middle unit towards a central axis of the string winding apparatus,

wherein the responsive protrusion protrudes in a perpendicular direction from the upper surface of the partition,

wherein the ratchet protrusion protrudes in a perpendicular direction from a bottom surface of the cover unit towards the responsive protrusion, and

wherein the second engaging portion is integral with the cover unit and only engages with the first engaging portion.