Someone who strikes hammer against metal while working (to ensure the surface of the hammer would remain smooth) is doing מכה בפשיש acc to r shimon ben gamliel bc it’s fixing the hammer. Tanna kamma says it’s not liable bc it’s done in the middle of work.

Plowing and sowing any amount is obligated in Shabbos. In the mishkan they would dig furrows for one stalk of herb needed for dye, and sometimes we plow a tiny amount before planting pumpkin seed.

Weeding is a form of sowing, and if someone plucks a tiny amount to help a tree/ground grow better, they are liable. If someone cuts wood/grass for usage, that is a form of “kotzer” and the size is larger. Even if ones intent is for usage, if it does inevitably improve the soil they are liable for sowing bc it’s a פסיק רישא. However, this is only in their own field where they are happy for the field to be improved, but if they take out from someone else’s field, where they are apathetic about growth in the field, they are exempt.

Someone who writes two letters with any inks in any language or any characters is obligated for writing on Shabbos. R Yosi holds that the obligation is not for letters but for any marks, bc in his view, they marked the kerashim in pairs when they transported them without writing letters.

Acc to r Yosi that the melocho is marking, one is liable for marking with either arm. Like the Rabanan that it’s writing letters, only writing with the dominant hand is liable (except for ambidextrous person who’s liable for both hands)

If someone intends to write a full pasuk and writes only one word, all Tanaim agree that he is still liable. If he writes only two letters, R shimon says he is exempt. Likewise, someone who intends to drill a hole through wood and does only a smaller amount is exempt acc to r shimon. The Rabanan disagree and claim that even when less is done than intended, one is obligated as long as what they’ve done is significant in its own right. So if someone intended to write שמעון and writes only the first two letters of שמ they are liable bc שם is a name.

This novelty that one is liable for שם משמעון May be only bc ש and מ are two different letters. If it’s a case of of someone intending to write ששך and they write only two ש, it’s a dispute between r Yehuda and rabbis is they are liable.

The case of שם משמעון requires further explanation bc the מ is different in שמעון than in שם. In shimon it is an open men and in shem it is a closed mem. How can it be considered that the first two letters were the same as his intent? The Gemara proves from here that the two forms of mem can be switched in a Torah or Tefillin and it’s still kosher and the subtle change is therefore insignificant. However, there is a tanna who disagrees and maintains that a Torah isn’t kosher if the form of the mem is applied incorrectly.

The two forms of mem existed at the time of the luchos but they were forgotten and the Nevi’im Had to reestablish which went in the middle of a word and which at the end.