I've never knit socks...but I worked on dpn's on several stocking hats this past winter. The final throes of the top of the hat required dpn's.
Here is what I did to prevent the ladder or gap:
When I got to the end of (and finished all the stitches) on dpn #1...instead of picking a new blank dpn to start knitting the stitches on dpn#2...I knit three extra stitches onto the same needle with the stitches from dpn#1...I then just moved them/slid them onto the new blank as 'already knit' stitches.
When we finish dpn#1 stitches...and they are on blank #1...we usually pick up a new blank #2 to begin knitting the stitches on dpn#2.
I don't. I knit 3 extras, and then slide them onto the new blank #2...and finish up with the remaining dpn #2 stithces.
Kinda like jostling them back and forth. But no ladders or gaps can form. :eyebrow:
Yeah well maybe it is more time consuming, but I really did get fast at it. And, no gaps!