Tying a headscarf on Shabbat

It's Shabbat morning and you're getting ready to go to the synagogue. You take out your new Shabbat headscarf and stand in front of the mirror to tie it. But wait a moment...

If you're Sephardi, you can tie your scarf, even with a double-knot, as long as you fully intend to untie the knots within the week, and you usually do so.

If you're Ashkenazi, you can make only a loose double-knot, and only on condition that you fully intend to untie the knots within 24 hours and usually do so. However, if you don't usually untie the knots the same day, you may not make even a loose double-knot even if you fully intend to untie the knots within 24 hours.

In summary –

Sephardic women – a double-knot is permitted, as long as it is untied within a week.

Ashkenazi women – only a loose double-knot is permitted and only if you regularly untie the knots on the same day.