What is the proper way to write a letter dalet? When the sofer writes a Sefer Torah, tefillin or mezuza, it is customary that he writes the dalet in a certain manner so that it should not be confused with other letters. For example, the top, horizontal line of the dalet, its "roof" (gag) is longer than the vertical line, so that the dalet should not be confused with a kaf sofeet.
Furthermore, the leg of the dalet, its "regel," does not connect to the right end of the upper, horizontal line, rather, it is slightly indented. This extra bit of line is called an ekev, literally a "heel." The ekev ensures that the letter is not confused with the letter resh. It is also customary to add a tail on the left side of the dalet; this is known as a "kotz." Finally, a "tag" is also drawn on the upper-right side of the letter, as it is customary to draw single tagim on the letters bet, dalet, hey, het, yud, and koof, often known by the acronym "bedek hayah."
Summary: When looking at a dalet on the klaf of Sefer Torah, tefillin or mezuzah, one should make sure that the upper line (roof) is longer than the vertical line (leg), and check that there is an ekev, a kotz, and a tag.
