What is a Zeres?
Rashi: A Zeres is half an Amah. 1
The distance between the small finger (Zeres) and the thumb that are both extended to their maximum.
What was Kaful`?
Rashi: It is folded over in front of him, over his heart. 1
Da'as Zekenim, Hadar Zekenim: There were two Choshens. The stones were fixed in the outer one; the inner one was stuck to it, lest the stones fixed in the settings get ruined. Toras Kohanim supports this. It says, perhaps just like it is double, also the Efod
Rashbam: It is like a pocket, into which they put the Urim v'Tumim (Pasuk 30).
What purpose did the pocket in the Choshen serve?
Why does the Torah not mention them here?
Ramban #1 (on Pasuk 30): The Torah deliberately curtails mention of them due to their mystical connotations. 1
Ramban #2: The Torah only mentions the Urim v'Tumim when instructing Moshe to place them inside the Choshen. It does not mention them earlier, because, neither the people, nor the craftsmen 2 had a hand in them - neither as regards the donation nor as regards making them. In fact, they were made either by Moshe in sanctity, based on a secret formula of which only Moshe was aware, or by Hashem Himself. 3
Seeing as four letters ('Ches', 'Tes', 'Kuf' and 'Tzadik' do not appear in the names of the twelve tribes, how could the Urim v'Tumim be guaranteed to answer all the questions that were put to it?
Ba'al ha'Turim (Pasuk 17): The words 'Avraham, Yitzchak, Ya'akov Shivtei Yeshurun' were added to the names of the tribes. 1
Chizkuni (21), Ba'al ha'Turim: Arranged in the following way, so that each stones contained six letters, making a total of seventy-two (Refer to 28:30:1:1*): Reuven - 'Alef'; Shimon - 'Beis; Levi - 'Resh' 'Hey' 'Mem'; Yehudah - 'Yud'; Yisachar - 'Tzadik'; Zevulun - 'Ches'; Dan - 'Kuf' 'Yud' 'Ayin' Kuf'; Naftali - 'Beis; Gad -'Shivtei'; Asher - 'Yud' 'Shin' 'Resh'; Yosef - 'Vav', Nun; Binyamin;
In which order were the names of the tribes engraved on the stones?
Targum Yonasan (Pesukim 17 - 20) and Rashi (21) 1 : It is the order in which they were born
Gur Aryeh (21): Even though "k'Soldosam" is written only about the Avnei Efod, since it says "Ish Al Shmo", it means in the order proper for them, i.e. the order in which they were born. See also Na'ar Yonasan.