Here is a review of the main Sock Tops I use in my sock making. I do variations from time to time, but mostly one of these:
Basic Mock Rib.
This is my work horse topper – I’ve made thousands of these! Its a 3:1 mock rib (every 4th needle removed). The sample pic is done on a 54 needle cylinder, and 4 doesn’t divide evenly, so I have two sets of 4:1 – one on each outside side of the yellow hash marks. Where the two sets of 4:1 go doesn’t make a difference. But I’m a creature of habit.
My usual pattern is to knit 40 rows, replace the missing needles, knit two more rows and then hang the hem.
The first row after replacing the needles picks up the yarn, and the second row knits it. The fact that you have a row that doesn’t complete the knit leaves little holes, or as I call them, decorative features.
On my pattern scribbles, I write this top as:
40; NI; 2; HH (translation: 40 rows, Needles IN, 2 Rows, Hang Hem).
Alternate Mock Rib

This is another 3:1 mock rib, this time done on the 84 needle cylinder.
The only difference in this topper is that I pick up the missing stitches when I replace their needles. To pick up the stitch I simply grab the purl of an adjacent stitch and hang it over the empty needle. That gives the next round something to knit into, so there are no holes.
It gives a less casual finish which some prefer. I use it for a dressier sock or a finer yarn, or just for a change in pace. It is also 40 rows and I write it as:
40, NI P/U, 2, HH. (P/U for Pick up stitches).
I could suffice with one row after the pick up instead of 2, but its that creature of habit thing again.
Humongous Mother Mock Rib

This is basically the same as the Alternate Mock Rib, but in this case I have knit 80 rows before replacing the missing needles. This sample is 3:1 knit at a loose tension on the 72 cylinder as the top of a knee sock. I pick up the stitches on this type of top, which I write down as”
80, NI, P/U, 2, HH.
Advantages of Mock Rib
A mock rib hem top provides elasticity which will keep the socks up, but it does this without the use of purl stitches.
Purl stitches can be a source of discomfort for people with diabetes, skin conditions or sensitivies, and such. The top is also reversible – that is to say you can fold it down if you like and still have ‘good side’ showing.
It has a hand made and more decorative (IMO) look. I might add that I don’t find this the case with skimpy mock rib tops – 40 rows give a nice proportion to the rest of the sock, and unless its a fancy edged sock, I find the short tops to look chintzy. (Also all IMO!)
Disadvantages of Mock Rib
I find the mock rib doesn’t have as much ‘give’ as a knit-purl rib. So if you are pushing the limits of the size of the sock, it might be less desirable.
The mock rib is double thickness. So in something like a hiking boot or a ski boot, if the hem top happened to be overlapping the tight-top of the boot – it might be an issue.
Pico Top

The pico top is a variation of the basic mock rib top.
This sample is knit 2:1 mock rib on the 54 cylinder. I knit 10 rows, then transfer stitch 1 onto needle 2 of each pair, knit one row (the pico row) knit 8 more, replace the missing needles, knit 2 more rows, hang the hem. (In this sample I picked up the stitches when I replaced the missing needles – you can do it either way.)
The pico row picks up the yarn on the empty needles and the first row following completes the stitches – this leave a hole as in the Basic Sock. But when we knit an equal number of rows AFTER the pico round, those holes end up on the fold of the hung hem and that’s what makes the little picos.
One little trick I do on this kind of top – I normally knit with my heel spring in action full time. In pico tops I disengage the heel spring for row #10 at the beginning, and for the pico row. Then I re-engage it at the completion of the pico row. This looser tension will give more pronounced little pico bumps.
I write this as:
10 (9, SP OFF), Pico, SP ON,8, NI, 2, HH (or I may add P/U after NI)
Beaded Pico

This is EXACTLY the same as the Pico Top. But when I get to the transfer stitches step, I pull the yarn from the stitch that I am transferring through the hold of a bead with a fine crochet hook and then hang the stitch on the needle. This works on the 54 cylinder for me, and the fact that I have loosened the tention the row before the pico row gives me the extra stretch I need to work the beads.
The beads can also be added after the fact onto a basic Pico Top, which is what I do with the 72 cylinder – I find the needles to close together to accommodate most beads on that cylinder. (I have a detailed post on that somewhere – I think on my old blog.)
The beads in this pic are bigger than what I normally use – ‘pony bead’ size, and so in this case I also left the heel spring disengaged for one more round after the beads were placed. But normally, I would:
10, (9, SP OFF), Pico/bead, SP ON, 8, NI, 2 HH.
1 x 1 Ribbed Sock Top

This a basic knit one, purl one sock topper.
The sample is knit on the 72 needle cylinder with 36 slot ribber attached.
Starting with all needles in the cylinder and knitting with scrap yarn – I put the ribber on the knitter and place every other stitch off a cylinder needle onto a ribber needle, and remove the emptied needles as I go. When all the ribbing stitches are in place I knit a few rounds before beginning my sock yarn, just to make sure everything is hunkey dorey.
I knit 1 row with the ribber engaged, then I turn it off and knit one row, then I turn it back on and knit 25 rows.
The one row one, one off, then back on thing gives a good selvedge edge that doesn’t curl AND won’t unravel.
25 rows is arbitrary, but its what works for me. Like with the mock rib tops – I find too few rows just doesn’t look right.
Generally speaking, I switch to full stockinette after knitting the 1×1 topper. I rarely, if ever, knit with yarn that doesn’t have a high wool content, so I don’t need the extra elasticity of running, say, a 3 x 1 rib down the leg. (But that’s not a topper issue anyway!)
R/O 1, R Off 1, R 25, knit
Advantages of a Ribbed Top
These tops have a lot of give, so a particular sock size would work for a broader range of folks, and in particular with a fuller leg size at the top end of a foot size range.
The top is a single layer of stitches thick, so more suitable for hiking or ski boots.
If knitting with low elasticity type yarns, this would give a better hold up – like cottons without elastic component, or (ugh) acrylics.
Disadvantages of a Ribbed Top
Unsuitable for people with pressure issues that come from purl stitches next to their skin.
To me the ribbed top is more ‘Sock’ than ‘Design Accessory’. I think this is in large measure because they look ‘machine made’ vs ‘hand made’. That being said – some guys folks don’t want design accessories on their feet!
Time wise, it takes a few minutes more to make – not significant – but if you drop a stitch you’re pretty much screwed as you can’t access the knitting with the ribber on top of the cylinder.
Addendum Aug 18 2010:
See this post for a 2 x 1 rib top done with the 36 ribber dial and 54 cylinder.