Further Applications of Kosev and Mochek – Writing and Erasing on Shabbos

The Halachos are based on the rulings of the Mishna Berura (MB) and Shmiras Shabbos Kehilchasa (SSK), reflecting Ashkenazi practice

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Opening Pages Which Are Stuck Together

Stuck with a foreign substance: If two pages of a book become stuck together eg with glue, food dirt etc on parts of the pages where there is writing, one may not separate the pages on Shabbos as this will lead to the writing being torn which is forbidden due to mochek, erasing.
- However, if the pages became stuck together in a way that separating them will not tear writing, such as if they are stuck at the bottom or top of the pages, ie not on areas of text, one may do separate them.
Pages never cut apart: Note that if the pages appear stuck together at their edges as they were never fully cut apart when the book was printed, one may not separate the pages, as this is effectively tearing them to make the book usable, which is forbidden due to any/all of koreia, mechatech and makkeh bepatish (MB 340:45, SSK 28:1, fn2).

If a book has letters, words or images on the edges of its pages (known as the for-edge, ie the side opposite the spine), the accepted practice is to permit opening and shutting the book on Shabbos, and not to consider this as if one is erasing or writing – given the book is made to be opened and shut we do not consider this a melacha, in a similar vein to it being permitted to open and shut a door (or retractable roof etc) without it being considered bone or soser (building or destroying), as this is the use it is made for.
- However, given some are strict about this, if one has another copy of the same book without such writing or images on the edges of its pages, one should use that copy on Shabbos (MB 340:17, SSK 28:2)

If a page of writing has torn into pieces, one may also be lenient to hold the pieces together to enable one to read them, if one doesn’t have another untorn copy of the writing.
However, one may certainly not stick the different pieces back together (SA 340:14, SSK 28:3).

Non interlocking: On Shabbos iIt is permissible to play games or make puzzles which involve placing letters, pictures, or parts of them next to each other to form whole words or pictures, so long as they are not held in place by being attached to a base and the pieces do not interlock.
Interlocking or attached to a base:Where the pieces are held in place by a base, or interlock (such as with many jigsaw puzzles), these may not be used on Shabbos due to kosev, writing.
- Children: However, given there are lenient opinions on the above, one need not prevent children from playing such games or making such puzzles (SSK 16:24, fn 66-67).
Games where one keeps scores: Any games where one keeps scores, and one typically does so by writing the scores down (eg regular scrabble), may not be played on Shabbos, lest one come to write (SSK 16:32).

One may not attach magnetic letters, images, or part of them to a magnetic board on Shabbos (SSK 16:24).

Children may not draw images or letters using an etch-a-sketch on Shabbos (SSK 16:23).

Where necessary, one may walk pass CCTV cameras whose images are being projected onto a screen when one has no interest in this being done (this is again a ‘psik reisha delo nicha leih’, an undesired definite consequence of an action has two leniencies versus the Torah prohibition as a) the image on the screen is not lasting and b) one’s ‘writing’ on the screen is being done in an unusual way, so this is permitted)
Most poskim, however, forbid one to intentionally show oneself in front of a CCTV camera, for example so that a person looking at the screen can see who one is before allowing one to enter (OS 15 fn 55, Dirshu 340:60).