Tefilin Shel Yad
Rear view. Tefilin for a right-handed person, Ashkenaz wrapping. In this configuration, the loop is on the same side as the knot. Sometimes the loop is much longer, but a short loop is halachicly preferable.
Since the act of tightening the retzu'ah can pull the "yud"-shaped knot away from the bayis, it is recommended to have a small piece of gid (sinew) holding the knot in place. The gid loops through the ma’avarta (not under the tefilin) and around the knot.
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