Vikkel Braid, also known as Estonian or Lateral Braid, has the appearance of a horizontal chain of stitches running across the top of, and perpendicular to, the underlying columns of stitches as shown in the photos below.
When incorporating this technique into a design, I had a trawl around the internet to see what different techniques can be used for working this braid, in particular for starting and finishing the braid when worked in the round , such as around a hat or cowl.
The basic braid is usually worked flat using the following steps:
- Using the cable cast-on method, cast on one stitch.
- With working needle behind work, knit through back loop of the second stitch on the passive needle, without dropping stitch off passive needle.
- Knit through front loop of first stitch on passive needle and slip both stitches off that needle.
- Slip the last stitch made back from working to passive needle, purlwise.
- Repeat steps 2 to 4 until there is 1 stitch remaining after step 3. Omit step 4 for this final stitch.
- Knit the final stitch and pass previous stitch over in order to cast off one stitch and retain the original stitch count.
Note: it is important to tighten the yarn at step 2 in order to prevent the row of stitches from becoming too loose. You could even use a smaller needle size to ensure the gauge of the braid row is the same as the remainder of the knitting. There are numerous tutorials available online which explain the Vikkel braid technique. Here is one from Shibui Knits. This one from Drops shows how to work the braid in two colours (note: it is also possible to work all the live stitches in one colour, just alternating two colours for the lateral braid stitches).
When working the braid in the round, it is necessary to modify the above steps in order to ‘close’ the beginning and end of the braid. Various online tutorials recommend slightly different variations.
In this video by While They Play Designs, Step 1 above (cast-on) is omitted and Steps 1 to 4 are repeated until all stitches of the round have been worked. A new stitch is picked up through the centre of the original lateral braid stitch and the final stitch of the round cast off over this new stitch (the new stitch is placed at the start of the round in order to keep the start and end of the round in the same place). This is version 1 in the photo below.
In this video by The Sweater Collective, a new stitch is cast on at Step 1. To join the braid, the original lateral braid stitch is picked up onto the passive needle, followed by step 4 then steps 2 & 3, before casting off the penultimate stitch over the final stitch. (I am wondering whether there should also be a second stitch bound off at some point to compensate for the original cast-on stitch at the beginning of the round?) This is version 3 in the photo below.
In this tutorial by Studio-Miranda.com, instead of Step 1, the last stitch of the previous round is slipped back to the passive needle before continuing with steps 2 to 4. After working to the end of the round, the last stitch is pulled through under the original lateral braid stitch and replaced onto the working needle. This is version 2 in the photo below.
In this video by Sockmatician, a new stitch is created as in Step 1 above. At the end of the round, the yarn is broken and a needle used to graft the final stitch to the start of the lateral braid in order to create a completely invisible join.
In another blog I saw, a new stitch is created at Step 1, then the final stitch of the round is simply cast off by passing it over the first stitch of the round before starting to work the next round.
Here are examples of some of these techniques worked:
The choice of method depends on just how invisible a join is desired. There are a few points to note:
a) any new stitches created must be compensated by an equivalent number of stitches being bound off in order to maintain stitch count.
b) 
if no new stitch is created at the start of the round then the lateral braid will cause the column of stitches below the first stitch of the round to bend towards the left and into the start of the lateral braid. As illustrated here, this may not be ideal – this example is shown above a section of ribbing.
c) be careful to ensure that the start and end of the round remains in the same place when replacing stitch marker after finishing the join in the braid.
Skein Reaction 