Now, this sponge bar is NOT for the Singer 120 (or similar 8mm machines) but is a skinny one from an old standard machine I have, a Kappa Model 10. The weather stripping is 1/8” x 3/8” with adhesive on one of the 3/8” sides. I used either 3/4” or 7/8” wide satin ribbon that would cover the foam on 3 sides. I stuck the one side to the adhesive that is already on the weatherstripping and used double-sided adhesive (it’s on a roll like tape but it’s just adhesive, no tape) for the other side. A really thin double-sided tape would probably work too. You could probably glue it too but, if you do, WAIT FOR THE GLUE TO DRY before putting it back into your machine!! 😀
I didn’t glue the foam down into the channel on mine since so much of it is inside of the metal slot. I used pliers to help squish the foam flatter to get it into the channel.
You can see in the next pic that mine is a little too short but still extends past the needles (you can see the dents from the needles in the upper left). I would suggest cutting it several inches too long and then trimming off any excess. Either sticking the ribbon on and/or getting it into the channel made it a bit shorter and I started with a piece only a bit longer than the bar.
If you’ve seen pics of sponge bars for other machines, they taper down at the ends. I first tried wrapping the end with scotch tape but it fits so tightly into my machine that it just peeled the tape off when trying to insert it. I squished the end down to give the same tapered effect and now that I’ve got one end pulled out from taking the pics I’m going to cut a bit off of the bottom corner of the foam so that I can push the very end down into the channel farther–this helps prevent the needles from catching the end of the foam while inserting.