Knitting in loose ends

Awhile back I was shown how to knit a loose end (or tail?) behind the work as you go by moving the end (tail) back and forth across the stitch being completed. For the life of me, I can’t seem to reproduce it. Any advice out there???

What you do is hold the tail end up for one stitch so that the yarn you are currently working with goes under the tail, then for the next stitch hold the yarn down so your current yarn goes over the tail end. You alternate this, up and down, for a good # of stitches, I’d say at least 10 stitches or so. Then you can cut the rest off.

I just repeat, ‘old over new, old over new…’ as in old yarn tail crossed over the new working yarn.