Rav permitted to make simple nets (for fish) on Chol ha'Mo'ed, but not fancy nets for catching birds, because the latter is a professional task.

R. Yehudah permitted to build an oven (in a non-professional manner) and to make sieves.

Question: A Beraisa says that everyone agrees that one may not build an oven.

Answer: On Chol ha'Mo'ed Sukkos, when the weather is cool and sometimes rainy, it is forbidden to make an oven, because it will not dry out in time for the holiday. On Chol ha'Mo'ed Pesach, when it is sunnier, it is permitted.

One may make a banister for a roof or balcony, but only in a non-professional manner.

Cracks (of an oven floor - Rashi; of a rooftop - others) may be repaired with a roller or by hand or foot, but not with a Mechlatzayim (a professional tool).

Hinges, sockets, lintels, locks and keys may be repaired on Chol ha'Mo'ed, provided the repair was not intentionally left to Chol ha'Mo'ed

Preserves (pickled foods, etc.) may be made only if they will be ready before the holiday is over.

Question: What is a "non-professionally" built banister?

Answer (Rav Yosef): Making a makeshift fence of bay branches and palm leaves.

Answer (Beraisa): Placing rocks without mortar.

Question: If a roller may be used, then it goes without saying that it may be done with the hand or foot. So why are hand and foot mentioned?

Answer: Actually a roller is forbidden. What the Mishnah means to say is: One may use only his hand and foot and through them attain the same effect as a roller.

Question: A Mishnah elsewhere says that Yochanan Kohen Gadol put an end to the sound of the hammer on Chol ha'Mo'ed Why, then, does the Mishnah permit these repairs?

Answer #1: Yochanan Kohen Gadol abolished only noisy banging, as against metal; the Mishnah is dealing with hammering against wood, which isn't so noisy.

This is rejected, because it is difficult to say that some kinds of hammer noise are permitted and others forbidden.

Answer #2 (R. Chisda): The repairs spoken of in the Mishnah are talking about repairs done with a Magal (which is permitted because it makes no noise at all - Rashi; or because it is an unusual way [Shinui] to do these repairs - others).

Answer #3 (R. Papa): The Mishnah predates the Takkanah of Yochanan Kohen Gadol.

Answer #4 (R. Ashi): The Mishnah about Yochanan Kohen Gadol holds like R. Yehudah (see below, 11b, #1, and 12a, #5), who requires Shinui when doing a Melachah on Chol ha'Mo'ed; our Mishnah holds like R. Yosi who does not require a Shinui (if it's a Davar ha'Aved).

(Ravina): Since we are accustomed to banging in nails in doorframes without a Shinui on Chol ha'Mo'ed, we obviously hold like R. Yosi.

First version of the story of the Badisa river.

One time the river overflowed, leaving many fish around, which the people went to gather up. Rava permitted them to pickle them.

Question: The Mishnah forbids pickling except for the holiday; here the pickling will not be ready for a long time.

Answer: It is permitted anyway, because since the fish were already acquired, it would be a great loss if they could not be preserved.

Second version:

Rava permitted the people to go take the fish in the first place, and then pickle them.

Question: As above, 5:a:2.

Answer: It is possible to eat pickled fish even before the pickling process is finished, by rinsing the fish many, many times. Thus, it is in fact possible to partake of them during the holiday.

Here the Gemara digresses into a discussion of various matters concerning the eating of fish.

If someone turned his olives over to prepare for pressing (and they will spoil if not pressed quickly), but he was unable to press them because he became a mourner or because his workers didn't show up or some other good excuse, R. Yehudah says he may do the minimum pressing to prevent the loss of the olives, and leave the rest for later.

R. Yosi says the entire process may be followed as usual. (Because once something is a Davar ha'Aved R. Yosi permits doing Melachah in the usual manner, without Shinui.)

The Mishnah says that the person was unable to press his olives because he became a mourner; in this case he is permitted to press them when Chol ha'Mo'ed arrives, because it is a Davar ha'Aved. R. Sheisha Breih Derav Idi infers from here that during the days of mourning Davar ha'Aved is not permitted.

Rav Ashi says that if Davar ha'Aved is permitted on Chol ha'Mo'ed, which is Mid'oraisa, then certainly it is permitted for the mourning period, which is mid'Rabanan. The reason the Mishnah doesn't mention it is that it's obvious.

There is a Beraisa that concurs with R. Sheisha's opinion. The Beraisa makes several points about the laws of mourners doing work:

If a mourner's olives urgently need pressing, others (but not he himself) may do it for him. The same is true for other cases of Davar ha'Aved. (This is the statement that proves R. Sheisha's opinion.)

(Rabban Shimon ben Gamliel): If there is no one else who can do the job the mourner can do it himself, in private.

(Rabban Shimon ben Gamliel): If the mourner is a professional whom the public needs (and there is no one else who can do his work) he may do his work.

If the mourner is a sharecropper or tenant-worker in a field, others should take his place in doing his farm work (to prevent loss to the field's owner).

A mourner who owns a moving company (he's a donkey-driver, a shipper, etc.) should not accept a new job, but if he already has an obligation from beforehand he can do it (to prevent loss to the client).

A worker who is paid by the day, if he becomes a mourner, should not work.

If the mourner does work for others in his own home (tailor, launderer, dyer, etc.), whether by contract or by the hour, he should not work.

If the mourner is having others do work for him in his house (e.g., renovations) they must not work. (But if their work is done elsewhere it's alright.)

Story: Mar Breih etc. had a partnership with Marion Breih etc. in a pair of oxen. Once, he became a mourner and did not let his ox go to work, thus causing a loss to his partner Marion, who could not manage with one ox.

Question: This contradicts 2:c:5, which says that a mourner may work if his refraining from work would cause a loss to others.

Answer: Mar held that an important Rabbi such as himself sometimes has to avoid leniencies that the Halachah technically permits (lest others learn from his actions to be even more lenient).