398. The Tefillin Straps

Tefillin, Mezuzah v’Sefer Torah 3:11

The grooves between the compartments of head tefillin should reach the stitching but if they don’t, the tefillin are still valid so long as the grooves are recognizable and four compartments are apparent. If the grooves are not recognizable, the tefillin are invalid. A thread or cord must be passed through each groove on the leather to separate the compartments. The common practice is to pass one of the sinews used to sew the tefillin between each of the grooves.

Tefillin, Mezuzah v’Sefer Torah 3:12

We use leather straps that are as wide as a barley-corn is long, or wider. The straps of the head tefillin must be long enough to go around the head, tie the knot, and continue on either side of the head until they reach the umbilicus, or slightly above it. The strap of the arm tefillin must be long enough to go around the forearm, tie the knot, and continue until it can be wrapped around the middle finger three times and tied. Straps longer than necessary are acceptable.