Based on a Naaleh.com shiur by Rabbi Shimon Isaacson
·Can you zip or unzip a sweatshirt with words on it on Shabbat? A problem arises with bringing together and breaking apart letters on the shirt much like a book with wording on the side. Therefore, it should be avoided if possible. One can be lenient in cases of necessity as per the Mishna Berura.
·Jigsaw puzzles that are meant to last may not be put together on Shabbat. Wooden picture puzzles where pieces are fitted into corresponding holes are permitted. Picture puzzles with a background are ok for children. Puzzles that are meant to be taken apart and are affixed to a surface may pose a problem. However if the pieces are on a cardboard background, one can posit that it is the same as affixing a background to a background, which is permitted. Nevertheless adults should avoid this if possible.
·Writing with icing on a cake violates the Rabbinic prohibition of Kotev. It follows that if one cuts through the letters, one is violating Mochek. One may not cut through icing with script writing as the letters are attached.
·Are biscuits with lettering ok to eat on Shabbat? The Maharam MiRottenberg prohibited this. Most Acharonim permit it on the basis that the Maharam ruled stringently in a specific case of biscuits which were meant to be erased/consumed as a Kabbalistic segula (good sign) for wisdom. Indeed the Dagel Merivava notes that it is permitted as one is eating the letters directly, there is no intention to erase, and the writing is temporary. Likewise, the Mishna Berura permits it as one is swallowing letters in the normal manner of eating.
·Are chocolate bars with imbedded words a problem? Here too, the letters are engraved in the bar and one breaks the words with one’s mouth and not with an instrument. The Chazon Ish, ruled stringently and prohibited it. The custom is to be lenient.
·A four- pack yogurt, which when attached form a complete picture, may not be broken apart on Shabbat.
·Food particles stuck to a bentcher may not be removed on Shabbat as one can come to pull letters off a page.
·Food packages with printed words or images should be opened before Shabbat. If one needs to tear them on Shabbat, one should be careful to tear where there are no letters or pictures or between the letters.
·Shoes with soles that leave a written imprint in the snow may be worn on Shabbat as the writing is unintentional.