I would just use masking tape. It's designed to come off surfaces without leaving a residue. Never write an article promoting some solution, without discussing

I would just use masking tape. It's designed to come off surfaces without leaving a residue. Never write an article promoting some solution, without discussing some alternative! There are possible issues with gummy glue; it can be stubborn in adhering to cards. Getting stubborn piece of gummy glue off the back of a tiny Micro SD card could be not fun. You don't want to require the user to excessively handle the card or put mechanical any stress on it. They are thinner and more delicate than credit cards (and the bulk of those is just plastic. Only the chip and the magnetic stripe are sensitive). Some users could end up trying to use a MicroSD with a piece of the gummy glue on it. I wouldn't want to put anything across the contacts of the SD card, which would mean that the adhesive would be on its back. But in that case, the contacts stick out of the page, inviting damage. Imagine the user clumsily shaking the letter out of the envelope, such that it it fall out, opens, lands with the SD card down, and is immediately stepped on by their five-year-old. If you put it on the paper contacts-down, you can tape over the back.