Women Wearing Prayer Shawls
Because the commandment is to see the threads and remember the commandments, the commandment is time-related (to see the threads in biblical times, one needed daylight, and therefore one had to perform the commandment during the daytime, making the commandment time-related). In general, women do not have to perform commandments that are limited by time. This does not mean that they cannot perform them. It is a matter of choice for women.
However there is also responsibility related to this choice. One should know what one is choosing. Because the prayer shawl holds the threads that are there to remind the wearer of the 613 commandments, one should know what the commandments are. Where one stands on the continuum of fulfillment of commandments is an individual matter. But one should be moving in the direction of fulfillment of them.
The sole purpose of the prayer shawl is the bearing of the corner threads. It is very important that the corner threads be tied correctly, and that they haven't become unraveled or untied.
If you use the prayer shawl and the corner threads are not tied correctly and completely, you are not performing the commandment as was intended.
If you have checked that the four sets of corner threads have five knots on each corner, you have done what is necessary. Usually if there is a problem, it is that the last knot and some twists have come undone. The fourth and last section of the corner threads of each corner has thirteen twists and then a double knot. Women are permitted to tie the corner threads, so you can correct what has come unraveled.
Refer to the section in Israelcraft entitled "The Tying of the Threads of a Prayer Shawl" to guide you further.
If you would prefer, ask your rabbi or someone in your congregation to help you, or call me, Marilyn Jackler, at Israelcraft, and I will guide you.