Does the left leg of the hei need to be under the edge of the roof?

The proper place to form the left leg of the letter hei is underneath the left edge of the letter’s roof. If it was not placed at the edge, the letter can be fixed--either by shortening the roof or by erasing and rewriting the leg. If the sofer is unable to fix it, the letter is kosher b’dieved if it was formed at least under the left half of the roof. There should be a noticeable space between the top of the leg and the roof of the letter. The left leg should be parallel to the right leg.

Where in the Torah is there a unique vav?

At the beginning of parshas Pinchos, the letter vav in the word sholom is supposed to be ketuah (severed). Some poskim explain that the leg of the vav should be cut off. Others explain that the proper method is to write a complete letter, but to make it smaller than the rest of the letters. Some Achronim say that it is preferable to sever the vav after the point that it is already recognizable as a vav. Doing so satisfies both views: the leg is cut and the vav is also written as a whole letter in a smaller font.

 אות ו ביאורים ומוספים דרשו 7

Which two letters form the letter ches?

According to many Rishonim, the proper way to write the letter ches is by writing two zayins and connecting their roofs with a bridge that has a pointed hump. The zayin on the right should be rounded at its upper right corner. According to the teachings of Kabbalah, the right side should be shaped like a vav when one is writing tefillin. If the ches is formed with either two vavs, a daled and a vav, or a daled and a zayin, it must be fixed and written properly. If it cannot be fixed, the letter is kosher b’dieved.