I didn't even think of looking in the glossary of terms on this site--it wasn't that I was unfamiliar with the term, it was that I'd never done it and also wasn't aware that there was an accompanying video.
I am so grateful for everyone's response. I was doing it the wrong way--slipping the RH needle through the back of the stitch properly, but the needle tip was ending up on the back side of the LH needle, not the front.
I am so happy now! Now I don't have to dread those 30-some-odd rows of my afghan block pattern that have the ssp decrease.