|This is a fast and easy way to mark hems on a swimsuit or a knit garment. This method keeps the knit from stretching while you mark the hem.
You need a clear ruler marked with at least 1/2 inch increments, a smooth tracing wheel (a toothed one will hack up the fabric) and some sewing tracing paper.
Place the tracing paper on your table with the marking side up, and place the the knit on top of that, RS up. Place the ruler at double your hem - for example, 1 inch for a 1/2 inch hem. Take the tracing wheel and roll along the ruler on the RS of the fabric, moving it as needed for a curved hem, if you have one.
The hem is now marked on the WS, and you can just fold up up the hem and secure with a glue stick. Sew your hem.
You should first test the tracing paper marking to make sure it washes out,