noun
tacking thread; basting thread
Thread used for temporary stitching (tacking/basting) in sewing, removed after final sewing.
仮縫いの前に、しつけ糸で布を留めます。
Before the temporary stitching, I hold the fabric in place with basting thread.
しつけ糸は後で抜くので、目立つ色を使うと便利です。
Since basting thread is removed later, using a conspicuous color is convenient.
しつけ refers to the act of basting or tacking, while しつけ糸 specifically means the thread used for that purpose.
Compound of しつけ (basting/tacking) and 糸 (thread). The exact derivation of しつけ is uncertain, but it is a sewing term for temporary stitching.