Yevamot, Chapter Twelve, Mishnah One
The twelfth chapter of Yevamot discusses how halitzah is performed. The first mishnah discusses the necessity of the presence of judges and what type of footwear she must remove from the yavam in order for the halitzah to be valid.
1) The commandment of halitzah must be performed in the presence of three judges, even though all the three are laymen.
2) If the woman performed the halitzah with a shoe, her halitzah is valid, [but if] with a felt sock it is invalid.
a) If with a sandal to which a heel is attached it is valid, but [if with one] that has no heel it is invalid.
b) [If the sandal was tied] below the knee the halitzah is valid, but if above the knee it is invalid.
Section one: In describing halitzah, Deuteronomy 25:7 states, And if the man does not wish to take his brother’s wife, then his brother’s wife shall go up to the gate to the elders, and say: ‘My husband’s brother refuses to raise up for his brother a name in Israel; he will not perform the duty of a husband’s brother unto me. From here it is clear that halitzah must be performed in front of elders, interpreted by our mishnah to refer to a court. However, there is no need for expert judges, and mere laymen will do. This is probably because this is a ceremony and not a true court case.
Section two: The Torah states that halitzah must be done with a shoe, which in the Torah refers to a leather shoe. Hence any kind of shoe made of leather is fit for halitzah, but not a shoe made of felt. In rabbinic Hebrew, a shoe is made of soft leather. A sandal which is made of hard leather is also acceptable for halitzah, provided that it have a heel.
Deuteronomy 25:9 states that she shall pull the sandal off his foot. According to our mishnah, if the sandals straps were tied below the knee, she can fulfill the requirement to pull the sandal off his foot. If the straps are above the knee, then this requirement is not fulfilled.
Others explain this last clause to refer to an amputee, that if his leg was cut off above the knee, halitzah cannot be performed, but if his leg was cut off below the knee halitzah may be performed.