Don't worry, this post isn't nearly as unfriendly as the title makes it sound. I'm talking about zig zag chains and lock stitch chains.
In all of today's samples, I had red thread on the shuttle and blue on the ball. For simplicity, I started all of them by just tying the two threads together in a Big Ugly Knot. Obviously, you would normally use standard techniques to begin without a knot and hide the ends.
A zig zag chain is made by alternating sets of flipped and unflipped double stitches. As with the second half of a split ring, you have to switch the order of half stitches when making the unflipped DS. Mark Meyers has a video of it here. Mark uses two shuttles in the video, but you can also do it with ball and shuttle. When you alternate flipped with unflipped DS, you are also alternating which thread is the core thread. You are essentially making a series of short chains going in opposite directions; hence the zig zag or rick rack effect. Here is a sample using sets of 4 flipped, 4 unflipped.
As Mark demonstrates, you can also put picots at the places where you switch, but I didn't in this case.
This technique is not very common, but there are a few patterns that use it. Rozella Linden (Ruth Perry) makes use of it in her book Celtic Tatting: A Design Journey on an Ancient Theme, and Mark uses it as a header in this edging. I also used it in my "Crazy Daisy" snowflake.
If you make a zig zag chain with only 1 flipped and 1 unflipped DS, the zigs and zags are so short that you basically get a straight line, something that a normal tatted chain doesn't do very well.
This is a useful technique where you need a straight line, such as a bookmark tail or the stem of a flower. I did this for the flower that I made the other day.
(Note: regarding the flower itself, I came up with the design on my own, but it turns out that it is basically the same as a Mary Konior pattern that I wasn't familiar with, "Wild Rose". Thanks, Suzanne, for pointing this out.)
Then there is the lock stitch chain. You know what a lock stitch is, right? It's just like a regular DS, except that you don't flip one of the half stitches; it doesn't matter which one. It's common to do it after you use a split ring to climb from one round to the next; you need a picot at the top of the SR to match all the other rings in the round, so you make a mock picot and begin the following chain with a lock stitch so that the core thread doesn't pull through the MP. Well, for a different effect, you can make a whole chain of lock stitches. As with the 1/1 zig zag chain, it makes a straight line (although either of them can be forced into a curve), and when using two colors, they both show up.
Jane Eborall has a snowflake here that uses lock stitch chains. I often use them for bookmark tails as well.
At first glance, the lock stitch chain looks similar to the 1/1 zig zag chain, but on closer examination you can see the difference. In the zig zag chain you can see the double stitches; on the lock stitch chain you can't because there aren't really any. The two colors interlock more closely, and the surface of the chain is slightly bumpier. The lock stitch chain is also a little bit thinner than the 1/1 zig zag and is therefore more flexible as well. This scan shows the two of them together.
These two types of chain can often be used interchangeably. Just be aware that they do give slightly different effects and choose the one that best suits your needs. As always, I encourage experimentation!