Rashi: That width of the interior of the opening. It was taught (Midos 2:3) that all the openings were 10 Amos wide.

Radak: The Mezuzos, thresholds and openings are all called Sha'ar. Only what is open is called Pesach. The width of the Pesach is 10; it does not tell its height. Ten does not include the [thickness of] the Safim, only the size of the opening.

Malbim: It is the width of the gate itself, from north to south.

Rashi: The interior of the Ulam, from north to south.

Rashi: Ten are for the interior of the opening, and one and a half Amos on each side. Do not be astounded that regarding the Pesach it is called width and regarding the interior of the Ulam it is called length. The Pesach, its height is its length, and its width is from Mezuzah to Mezuzah. The Ulam, since the amount its interior juts out from east to west (8) is less than its interior from north to south (13), the bigger Midah is called length. We find like this regarding Bayis Rishon ? "veha'Ulam Al Pnei Heichal ha'Bayis Esrim Amah Arko Al Pnei Rochav ha'Bayis" (Melachim I, 6:3). From north to south is called width for the Heichal, and length for the Ulam, since the Heichal is longer from east to west than from north to south, and oppositely for the Ulam.

Radak, Vilna Gaon, Malbim: It is from the outer Saf to the end of the inner Saf, from east to west. Radak - the outer Saf was Kaneh, i.e. six Amos wide; now it is called length, for from one end to the other, it is the bigger measure. Also the outer Saf was six, and there was one Amah between them.