Inserting the thread leftover into the sewing stitches in order to prevent the thread leftover escaping from end of sewing. For sewing underwears, sleeves of sportswear, and side hemming.

BK: Back Latching Device

REMARK
1. 4 threads BK has two kinds of Needle plate.
E591F-suitable for medium heavy to heavy fabrics/ E591B-suitable for light materials.
2. This model can be attached with "Needle Locating Motor" whereas the pulley should be changed to KD35