Why knitted garments need special care
Knitted fabric is built from interconnected loops. Cutting across those loops can cause the fabric to ladder or unravel unless the edge is secured using a method suited to the garment's construction.
The safest approach depends on the knit, yarn, seams, hem finish and garment design. A general online instruction cannot account for every sweater or machine-knit structure.
Assess the garment before altering
Inspect how the hem is made, where seams sit and whether the garment has a rib band or shaped edge. Consider how much length must be removed and how the finished proportions will look.
If the sweater is valuable, delicate, or has a complex construction, consult a professional alterations specialist who can inspect it in person. Avoid cutting before the method and finishing have been confirmed.
A note on the original tutorial
The source title presents a professional step-by-step guide, but alteration outcomes are garment-specific. This translated summary deliberately does not provide cutting instructions that could damage a garment.
Test any proposed technique on a matching swatch or an inconspicuous area only with appropriate expertise; seek professional advice for the actual item.