||I had asked a while back this question on Post-It Notes:
E-mail: not available
Date: 12/14/2003 2:50:00 AM
Message: Can you use post its and other stickers on shabbat? For example, to keep your place in a sefer if you are going to be flipping back and forth from page to page. Does it matter if the sticker is permanent or temporary like a post-it? Someone told me it was an issur of sewing which made no sense to me....
Reply: You are right! It is OK.
But recently saw this information, see below. What is Rav Abadi's basis for allowing Post-its ? Are there any restrictions on his hetter ? Please review the below and clarify exactly is allowed and what is prohibited.
From yeshiva.org.il in the English Section of Ask the Rabbi --
Gluing papers one to another is a Torah prohibition a Toladah (derivative) of Tofer (sewing). If the gluing is not permanent, it not a problem of Tofer on Shabbat. Non-permanent for that matter is till the end of Shabbat but if planned to stay longer – it stops being non-permanent. (Shulchan Aruch OC 340, 14; MB ibid 45; MB 314, 44)
The Shmirat Shabbat Kehilchata (9, note 19) explains the notion to mean that only if it forms one body by gluing it, but not for instance if only the edge of the bag is glued like in plastic wrappers.
The Shmirat Shabbat brings more (in note 77) that only gluing two pieces of paper together it will be Tofer but if gluing a paper to a hard solid thing i.e. a sticker to a bottle it will not be prohibited as they don’t join together the same way as two papers.
Therefore one should distinguish the way post-it sticker is used.
If it is posted on paper for a long period – it should not be done on Shabbat (as I wrote in the previous Responsa)
If it will be use only temporarily for that Shabbat or on a solid surface (table, glass) it seems to be permitted.