Tav, the final letter of the Hebrew alphabet. Tav is the sign or seal of a covenant. It was often used as a mark in the same sense as our signature is today, especially of those who could not read or write. Conceptually, tav is a wounding, as the sealing of a covenant required the wounding of the sacrifice, whose blood sealed the covenant. It resembles a doorpost, as the blood was applied on in Mitzraim (Egypt), thus sealing that household and sparing them from the tragedy of the firstborn.