The trouble with knitting socks for small people is that their feet grow. Which may not be trouble really - it's quick to knit small socks, and if the feet are small enough, the person who operates them may forget about handknit socks by the time their feet are large enough to need a new pair. Also, there may be upcoming small feet to take on the use of the socks until they are, finally, more hole than fabric.
But if you are not mindful, and over-generously knit socks for a cold-footed not-so-small person with a sibling who will inevitably also want a pair, you may find yourself with a pair of Sock Monsters.
And then, when their feet outgrow the socks you made them last winter and the weather is already growing cold for the next one, you might find yourself sitting down with scraps and some scissors.
Now, I don't know that I recommend trying this. My original plan was simply to take the socks back once they were outgrown (I only knit them in the first place because they both happened to take my own sock size - it's not like I have a heart or anything) and really, even light wear inside winter boats is going to produce enough felting on the inside of the sole to make ripping out and reknitting the foot a bit longer, more than a bit of a chore.
But it's such an interesting chore. And much faster than knitting an entirely new pair of socks with ribbing (because the monsters' legs are too narrow to hold the socks up otherwise.)
Basically, you have to rip out the grafted toe of a top-down sock - if you were the slightest bit sloppy about how you ran in the end after grafting, the tail is easier to find - and peel back the yarn to the start of the toe decreases.
Then, you get the live stitches back onto needles, placing them carefully so the heel gusset lines up with the original needle arrangements. Otherwise, you'll have an off-centre toe.
I found that picking up the stitches with a set of very sharp tipped needles a size down, and then shifting them onto the original ones, makes that job much easier.
After all that you just knit onward, in pattern.
I added an extra 10 rounds, which put the final sock length at the outside border of what currently accommodates the relevant sock monster (and, coincidentally, the outside of what always fits me - because I am not doing this again to these socks; I don't think the yarn could stand it, never mind the knitter.)
I do not, incidentally, recommend knitting the new length with the old yarn. I did it for this sock and will have to do it for its mate, but the stitches don't lie as neatly, and as I mentioned - the yarn is a bit tired after the previous winter's use.
When it's time, start a new toe.
And when that's done, say YAY! as loudly as you can...
... and get on to the next three socks. le sigh.