I received an email from a lady who had attended one of my little workshops about 12-15 years ago. One of the small how-to's I showed was putting a Pulling Thread into a casing as you knit. I no longer have the handouts available (2 computer crashes in the ensuing 12+ years) so while I was knitting the other day, I took a few pics as I was doing the casing. If you need additional details, please feel free to email me.
When I need to pull elastic or ribbon through a narrow casing, I do it while I'm closing the casing on the machine. This example has waste yarn, then ravel cord and then 6 rows - it needed to be very narrow for the elastic I was using in that project.
The thread in there is what I call the Pulling Thread. My Mom called it that in her sewing so I've always just used that term. I don't know how many times she'd be sewing a casing and lay a piece of yarn or cording in there before sewing.
I laid the Pulling Thread in the 'trough' between the stitches on the machine and the stitches I was hanging onto the same needles when closing the casing. Keep the Pulling Thread in the trough as you go along, making sure you do NOT let it catch on the needles or with the yarn. Every once in awhile, I'll pause my work and make sure the Pulling Thread is still free of any catches by taking both ends and sliding it back and forth.
It's a LOT easier to correct any issues with the Pulling Thread as you go along rather to find out once you take the work off the machine that OOPS!, it's caught!! Once you're done, just attach your elastic or ribbon or whatever to one end of the Pull Thread and you'll be able to easily pull it through your casing.
~ Marge ~