How were the Lechem ha'Panim shaped?
Rashi and Ramban #1 on Pasuk 30, according to the first opinion in Menachos, 94b): They were made 'in the shape of a box' with the two long sides removed, 1 the length of the loaf straddling the width of the Shulchan (each of the two rows of six loaves taking up half the length of the Shulchan).
Ramban #2 (on Pasuk 30) according to the second opinion in Menachos (Ibid.): They were made in the shape of 'a rocking boat' (like the letter 'v').
Like an upside-down 'Ches' (Sifsei Chachamim).
What were the Ke'aros and the Kapos?
Rashi, Rashbam, Targum Onkelos and Targum Yonasan: The Ke'aros were two sets of forms into which the loaves were to be placed, one (made of iron) in which the dough was baked, the other (made of gold), into which they were placed on the Shulchan after they were baked; the Kapos, the two spoons 1 into which the Levonah (the frankincense that accompanied the Lechem ha'Panim) was placed. 2
Hadar Zekenim: The Ke'aros were bowls in which the bread was kneaded.
And what were the Kesavos and the Menakiyos?
Rashi #1 (citing Targum Onkelos), Rashbam and Targum Yonasan 1 : The Kesavos were golden half-canes (split lengthways) 2 which divided between the layers of Lechem ha'Panim, fitted in grooves in the Menakiyos - three on top of each loaf [Rashi]) to support one layer of loaves; 3 whereas the Menakiyos were posts 4 that were erected along the length of the Shulchan, and protruded way above it - in which they made grooves to hold the Kesavos 5
Hadar Zekenim: The Kesavos were Kelim from which they poured water onto the flour to knead it.
According to Rashi's understanding of Targum Onkelos - that 'Mechilaseih' (Onkelos' translation of "Menakiyosav") means 'contained' - since they contained the golden half-canes.
So-called because it has connotations of 'hollow (in Arabic, whatever is hollow is called Kasva' [Rashi]).
To allow a flow of air between the rows of loaves, to prevent them from going moldy (Rashi). See Rashi for more details.
Shaped like forks (Rashbam).
Thereby preventing them from weighing down on the loaves beneath them and causing them to break (Rashi).
So-called from the expression 'Kasheh', because they caused the loaves to remain hard and not break.
So-called because they kept the loaves clean - by preventing them from going moldy.
What is the meaning of "Asher Yusach bahen"?
Rashi and Rashbam: It refers to the Kesavos, which covered the loaves like S'chach. 1
Rashi writes that each post had six grooves to hold the Kanim that divided between the loaves. Five should suffice, for one loaf rests on the Shulchan!
Riva: The top groove held pegs that supported the spoon of Levonah on top of each stack of loaves.
Mizrachi: 'Six' is a scribal error. The correct text is 'five.' Menachos 97a says that there were 14 Kanim - the top bread rested on two, the four loaves in the middle rested on three each, and the bottom bread rested on the Shulchan!