It’s impossible to mark your own hem without a helper. You can take your chances and simply fold up an even amount of hem allowance all around, but you’re likely to end up with a hemline that hangs crookedly on the body.

If you don’t have a hem-marking tool, try this tip to mark an even, horizontal line on a garment.

Set up the string

Find a convenient doorway. Cut a length of string about a foot or two longer than the doorway’s width.

Coat the string with chalk powder. You can get this at Joann.com or CreateForLess.com. Although you can use powdered chalk intended for chalk lines used in home construction, the colors are more intense and may not be easy to remove after the hem has been sewn.

At each door jamb, measure up from the floor to the desired hem height. Tape an end of the string to each door jamb at this height, stretching the string taut. With a level or a ruler, check that the string is level.

Mark the hem

Put on the garment that needs hemming. Stand close to the string, and turn slowly, letting the garment brush lightly against the string. This transfers the chalk to the garment in an even line. The chalk marks the hem’s foldline. Take off the garment, press up the hem allowance along the chalk line, and sew the hem.

For a refresher on how to sew a hem, watch “How to Hem,” with Judith Neukam.